Imaging lens and imaging apparatus

ABSTRACT

An imaging lens consists essentially of six lenses in the following order from the object side: a negative first lens; a positive second lens; a negative third lens; a positive fourth lens; a positive fifth lens; and a negative sixth lens. Conditional expression (1) is satisfied, wherein f is the focal length of the entire system, and f5 is the focal length of the fifth lens: 
       2.38&lt; f 5/ f   (1).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/JP2013/004085 filed on Jul. 2, 2013, which claims priority under 35U.S.C. §119(a) to Japanese Patent Application No. 2012-162664 filed onJul. 23, 2012. Each of the above applications is hereby expresslyincorporated by reference, in its entirety, into the presentapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging lens and an imagingapparatus, and more particularly to an imaging lens suitable for use ina vehicle mounted camera, a portable terminal camera, and a surveillancecamera that utilize an image sensor, such as CCD's (Charge CoupledDevice), CMOS's (Complementary Metal Oxide Semiconductor), and the likeas well as to an imaging apparatus equipped with this imaging lens.

2. Description of the Related Art

In recent years, image sensors such as CCD's, CMOS's, and the like haveachieved significant miniaturization and increased numbers of pixels.Accompanying these developments, as the bodies of imaging devicesequipped with these image sensors also have achieved miniaturization,there is demand for imaging lenses to be mounted therein to beminiaturized in addition to having favorable optical performance.Meanwhile, there is demand for imaging lenses to be applied for use in avehicle mounted camera, a surveillance camera, and the like to beminiaturized, be capable of being configured at low cost, and to havewider angles of view and higher performance. Japanese Unexamined PatentPublication Nos. 2009-216858, 2010-107531 and 2010-072622 proposeimaging lenses of a six-lens configuration, in which a negative lens, apositive lens, a negative lens, a positive lens, a positive lens, and anegative lens are arranged in this order from the object side, asimaging lenses to be mounted on vehicle mounted cameras.

SUMMARY OF THE INVENTION

Requirements for imaging lenses to be mounted on vehicle mountedcameras, surveillance cameras, and the like are becoming rigorous yearto year in such a manner that back focus is required to be secured inaddition to achieving further miniaturization, lower costs, wider anglesof view and higher performance.

The present invention has been developed in view of the foregoingcircumstances. The object of the present invention is to provide animaging lens which is capable of achieving miniaturization, low costs, awider angle of view and high performance, and securing of back focus aswell as an imaging apparatus equipped with this imaging lens.

A first imaging lens of the present invention consists essentially of afirst lens having a negative power, a second lens having a positivepower, a third lens having a negative power, a fourth lens having apositive power, a fifth lens having a positive power, and a sixth lenshaving a negative power in this order from the object side, and

the imaging lens satisfies conditional formula (1) below:

2.38<f5/f  (1), where

f: the focal length of the entire system, andf5: the focal length of the fifth lens.

A second lens of the present invention consists essentially of a firstlens having a negative power, a second lens having a positive power, athird lens having a negative power, a fourth lens having a positivepower, a fifth lens having a positive power, and a sixth lens having anegative power in this order from the object side, in which an aperturestop is disposed more toward the object side than the image-side surfaceof the fourth lens, and

the imaging lens satisfies conditional formula (2) below:

−4.1<R1/f<0.0  (2), where

f: the focal length of the entire system, andR1: the radius of curvature of the object-side surface of the firstlens.

A third imaging lens of the present invention consists essentially of afirst lens having a negative power, a second lens having a positivepower, a third lens having a negative power, a fourth lens having apositive power, a fifth lens having a positive power, and a sixth lenshaving a negative power in this order from the object side, in which anaperture stop is disposed more toward the object side than theimage-side surface of the fourth lens, and

the imaging lens satisfies conditional formula (3) below:

0<f4/f5<0.45  (3), where

f4: the focal length of the fourth lens, andf5: the focal length of the fifth lens.

The imaging lens of the present invention consists essentially of sixlenses. However, lenses substantially without any refractive power;optical elements other than lenses such stops, cover glasses and thelike; lens flanges; lens barrels; image sensors; and mechanicalcomponents such as image stabilization mechanisms may be included inaddition to the six lenses.

Further, in the present invention, surface shapes of lenses, such as aconvex surface, a concave surface, a planar surface, biconcave,meniscus, biconvex, plano-convex, plano-concave, and the like; and signsof the refractive powers of lenses, such as positive and negative,should be considered in a paraxial region if aspheric surfaces areincluded therein, unless otherwise noted. Moreover, in the presentinvention, the sign of the radius of curvature is positive in the casethat a surface shape is convex on the object side, and negative in thecase that the surface shape is convex on the image side. The expression“the center of the lens surface has a positive power” intends to meanthat a value of a paraxial radius of curvature is such that the lenssurface forms a convex surface. Further, the expression “the center ofthe lens surface has a negative power” intends to mean that a value of aparaxial radius of curvature is such that the lens surface forms aconcave surface.

Note that in the first imaging lens through the third imaging lens ofthe present invention, the materials of the third lens, the fourth lens,the fifth lens, and the sixth lens may be plastic.

Further, in the first imaging lens through the third imaging lens of thepresent invention, an aperture stop may be provided between theobject-side surface of the second lens and the image-side surface of thefourth lens.

Further, in the first imaging lens through the third imaging lens of thepresent invention, the object-side surface of the fourth lens is anaspherical surface, both of the center and the edge of the effectivediameter have a positive power, and the positive power at the edge ofthe effective diameter is weaker than that of the center.

The expression “having a positive power at the edge of the effectivediameter” means having a convex shape at the edge of the effectivediameter. The expression “having a negative power at the edge of theeffective diameter” means having a concave shape at the edge of theeffective diameter.

The expression “a shape in which a power at the edge of the effectivediameter is weaker than that of the center” means “a shape in which apower at the edge of the effective diameter is weaker than that of thecenter” both in cases where the power is positive and where the power isnegative.

In the first imaging lens through the third imaging lens of the presentinvention above, it is preferable for conditional formulas (4) through(12) to be satisfied. Note that preferably, the imaging lens may have aconfiguration, in which any one of conditional formulas (4) through (12)below is satisfied, or may have a configuration in which an arbitrarycombination of two or more of the conditional formulas are satisfied.

f56/f<−6.4  (4)

f34/f56<0.0  (5)

0.0<f34/f  (6)

2.0<f3456/f  (7)

0.9<νd2/νd3  (8)

−2.5<f3/f<−0.5  (9)

−3.0<f3/f4<−0.2  (10)

0.2<f12/f<5.0  (11)

(Nd1+Nd2+Nd3+Nd4+Nd5+Nd6)/6<1.70  (12), where

f: the focal length of the entire system,f3: the focal length of the third lens,f4: the focal length of the fourth lens,f12: the combined focal length of the first lens and the second lens,f34: the combined focal length of the third lens and the fourth lens,f56: the combined focal length of the fifth lens and the sixth lens,f3456: the combined focal length of the third lens, the fourth lens, thefifth lens and thesixth lens,Nd1 through Nd6: the refractive indices of the materials of the firstlens through the sixth lens with respect to the d-line,νd2: the Abbe number of the material of the second lens with respect tothe d-line, andνd3: the Abbe number of the material of the third lens with respect tothe d-line.

The imaging apparatus of the present invention is mounted with at leastany one of the first imaging lens through the third imaging lens of thepresent invention described above.

According to the first imaging lens of the present invention, a powerarrangement, and the like in the entire system are suitably set in alens system constituted by the minimum number of lenses, i.e., sixlenses, and conditional formula (1) is satisfied. This realizes animaging lens which is capable of achieving miniaturization, low cost,and a wider angle of view, and which has having high optical performanceby which back focus can be secured, various aberrations can be favorablycorrected and fine images can be obtained through the peripheralportions of the imaging area.

According to the second imaging lens of the present invention, a powerarrangement, an arrangement of an apertuere stop, and the like in theentire system are suitably set in a lens system constituted by theminimum number of lenses, i.e., six lenses and conditional formula (2)is satisfied. This realizes an imaging lens which is capable ofachieving miniaturization, low cost, and a wider angle of view, andwhich has high optical performance, by which back focus can be secured,various aberrations can be favorably corrected, and fine images can beobtained through the peripheral portions of the imaging area.

According to the third imaging lens of the present invention, a powerarrangement, an arrangement of an aperture stop, and the like in theentire system are suitably set in a lens system constituted by theminimum number of lenses, i.e., six lenses, and conditional formula (3)is satisfied. This realizes an imaging lens which is capable of securingback focus while achieving miniaturization, low cost, and a wider angleof view; and having high optical performance by which variousaberrations can be favorably corrected and fine images can be obtainedthrough the peripheral portions of the imaging area.

According to the imaging apparatus of the present invention, the imagingapparatus is provided with the imaging lens of the present invention.This enables the imaging apparatus to be configured in a small size andat low cost, to perform photography at a wide angle of view, and toobtain favorable images having high resolution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a lens configuration and optical paths ofan imaging lens of one embodiment of the present invention.

FIG. 2 is a view for explaining a surface shape and the like of thefourth lens.

FIG. 3 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 1 of the present invention.

FIG. 4 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 2 of the present invention,

FIG. 5 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 3 of the present invention.

FIG. 6 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 4 of the present invention.

FIG. 7 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 5 of the present invention.

FIG. 8 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 6 of the present invention.

FIG. 9 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 7 of the present invention.

FIG. 10 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 8 of the present invention.

FIG. 11 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 9 of the present invention.

FIG. 12 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 10 of the present invention.

FIG. 13 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 11 of the present invention.

FIG. 14 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 12 of the present invention.

FIG. 15 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 13 of the present invention.

FIG. 16 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 14 of the present invention.

FIG. 17 is a cross-sectional view illustrating the lens configuration ofan imaging lens of Example 15 of the present invention.

A through D of FIG. 18 respectively illustrate aberration diagrams ofthe imaging lens of Example 1 of the present invention.

A through D of FIG. 19 respectively illustrate aberration diagrams ofthe imaging lens of Example 2 of the present invention.

A through D of FIG. 20 respectively illustrate aberration diagrams ofthe imaging lens of Example 3 of the present invention.

A through D of FIG. 21 respectively illustrate aberration diagrams ofthe imaging lens of Example 4 of the present invention.

A through D of FIG. 22 respectively illustrate aberration diagrams ofthe imaging lens of Example 5 of the present invention.

A through D of FIG. 23 respectively illustrate aberration diagrams ofthe imaging lens of Example 6 of the present invention.

A through D of FIG. 24 respectively illustrate aberration diagrams ofthe imaging lens of Example 7 of the present invention.

A through D of FIG. 25 respectively illustrate aberration diagrams ofthe imaging lens of Example 8 of the present invention.

A through D of FIG. 26 respectively illustrate aberration diagrams ofthe imaging lens of Example 9 of the present invention.

A through D of FIG. 27 respectively illustrate aberration diagrams ofthe imaging lens of Example 10 of the present invention.

A through D of FIG. 28 respectively illustrate aberration diagrams ofthe imaging lens of Example 11 of the present invention.

A through D of FIG. 29 respectively illustrate aberration diagrams ofthe imaging lens of Example 12 of the present invention.

A through D of FIG. 30 respectively illustrate aberration diagrams ofthe imaging lens of Example 13 of the present invention.

A through D of FIG. 31 respectively illustrate aberration diagrams ofthe imaging lens of Example 14 of the present invention.

A through D of FIG. 32 respectively illustrate aberration diagrams ofthe imaging lens of Example 15 of the present invention.

FIG. 33 is a view for explaining an arrangement of a vehicle mountedimaging apparatus according to the embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

[Embodiment of the Imaging Lens]

First, the imaging lens according to the embodiment of the presentinvention will be described referring to FIG. 1. FIG. 1 is a viewillustrating a lens configuration and optical paths of an imaging lens 1according to the embodiment of the present invention. Note that theimaging lens 1 shown in FIG. 1 corresponds to an imaging lens accordingto Example 1 of the present invention to be described later.

In FIG. 1, the left side of the figure is the object side, and the rightside thereof is the image side. In addition, FIG. 1 also shows axialrays 2 from an object point at an infinite distance and off-axis rays 3,4 at a full angle of view 2ω. Further, FIG. 1 shows an image sensor 5disposed on the imaging plane Sim which includes an image point Pim ofthe imaging lens 1, taking the case of applying the imaging lens 1 to animaging apparatus into consideration. The image sensor 5 converts anoptical image formed by the imaging lens 1 into an electric signal. ACCD image sensor, a CMOS image sensor, or the like may be employed asthe image sensor, for example.

When the imaging lens 1 is applied to the imaging apparatus, it ispreferable for a cover glass, a low-pass filter, an infrared cut filter,or the like to be provided according to the configurations of a cameraon which the lens is mounted. FIG. 1 illustrates an example in which aplane parallel optical member PP that presumes such components isprovided between the most-image-side lens and the image sensor 5 (theimaging plane Sim).

First, the configuration of the first embodiment of the presentinvention will be described. The imaging lens according to the firstembodiment of the present invention includes a first lens L1 having anegative power, a second lens L2 having a positive power, a third lensL3 having a negative power, a fourth lens L4 having a positive power, afifth lens L5 having a positive power, and a sixth lens L6 having anegative power in this order from the object side. In the example shownin FIG. 1, an aperture stop St is disposed between the second lens L2and the third lens L3. Note that the aperture stop St shown in FIG. 1does not necessarily represent the size or shape thereof, but representsthe position thereof on the optical axis Z.

Further, the imaging lens of the first embodiment is configured tosatisfy conditional formula (1) below:

2.38<f5/f  (1), where

f: the focal length of the entire system, andf5: the focal length of the fifth lens L5.

Satisfying the lower limit defined by conditional formula (1) enablesthe power of the fifth lens L5 to be suppressed, and facilitatessecuring back focus and correcting field curvature and comaticaberration. Securing a sufficient amount of back focus facilitatesdisposing various types of filters, a cover glass, or the like betweenthe lens system and the image sensor as well as facilitating setting theexit pupil position far from the imaging plane. Thereby, suppressing theangles at which the peripheral rays enter the image sensor will befacilitated, resulting in facilitating suppression of shading.

Constituting the imaging lens of the first embodiment by the minimumnumber of lenses, i.e., six lenses enables low cost and reduction in thetotal length in the direction of the optical axis to be achieved.Further, an imaging lens which has high optical performance, by whichback focus can be secured, various aberrations can be favorablycorrected and fine images can be obtained through the peripheralportions of the imaging area, can be realized.

Next, the configuration of the second embodiment of the presentinvention will be described. The imaging lens according to the secondembodiment of the present invention includes a first lens L1 having anegative power, a second lens L2 having a positive power, a third lensL3 having a negative power, a fourth lens L4 having a positive power, afifth lens L5 having a positive power, and a sixth lens L6 having anegative power in this order from the object side. Further, in anexample shown in FIG. 1, an aperture stop St is disposed more toward theobject side than the image-side surface of the fourth lens L4, moreparticularly between the second lens L2 and the third lens L3.

Further, the imaging lens of the second embodiment is configured tosatisfy conditional formula (2) below:

−4.1<R1/f<0.0  (2), where

f: the focal length of the entire system, andR1: the radius of curvature of the object-side surface of the first lensL1.

Satisfying the upper limit defined by conditional formula (2) enablesthe object-side surface of the first lens L1 to be made a concavesurface, and facilitates increasing the power of the first lens L1,securing back focus, and reducing the size of the lens system in theradial direction. Satisfying the lower limit defined by conditionalformula (2) facilitates preventing the radius of curvature of theobject-side surface of the first lens L1 from excessively decreasing,and facilitates suppressing distortion and preventing the total lengthfrom becoming too long.

Constituting the imaging lens of the second embodiment by the minimumnumber of lenses, i.e., six lenses enables low cost and reduction in thetotal length in the direction of the optical axis to be achieved. Inaddition, as the aperture stop St is disposed more toward the objectside than the image-side surface of the fourth lens L4, reducing thediameter of each lens will be facilitated. Further, an imaging lens thathas high optical performance, by which back focus can be secured,various aberrations can be favorably corrected and fine images can beobtained through the peripheral portions of the imaging area, can berealized.

Next, the configuration of the third embodiment of the present inventionwill be described. The imaging lens according to the third embodiment ofthe present invention includes a first lens L1 having a negative power,a second lens L2 having a positive power, a third lens L3 having anegative power, a fourth lens L4 having a positive power, a fifth lensL5 having a positive power, and a sixth lens L6 having a negative powerin this order from the object. Further, in the example shown in FIG. 1,an aperture stop St is disposed more toward the object side than theimage-side surface of the fourth lens L4, more particularly between thesecond lens L2 and the third lens L3.

Further, the imaging lens of the third embodiment is configured tosatisfy conditional formula (3) below:

0<f4/f5<0.45  (3), where

f4: the focal length of the fourth lens L4, andf5: the focal length of the fifth lens L5.

Satisfying the upper limit defined by conditional formula (3)facilitates causing the power of the fourth lens L4 to be greater thanthat of the fifth lens L5. Increasing the power of the fourth lens L4facilitates correcting chromatic aberration between the third lens L3and the fourth lens L4 and enables the power of the fifth lens L5 to besuppressed. Further, securing back focus will be facilitated, andcorrecting field curvature and comatic aberration will be facilitated aswell. Setting the value of the lower limit defined by conditionalformula (3) to be 0 will cause the power of the fourth lens L4 to becometoo strong or the power of the fifth lens L5 to become too weak,resulting in correction of spherical aberration becoming difficult.Satisfying the lower limit defined by conditional formula (3)facilitates suppressing the power of the fourth lens L4 or preventingthe power of the fifth lens L5 from becoming too weak, resulting incorrection of spherical aberration being facilitated.

Constituting the imaging lens of the third embodiment by the minimumnumber of lenses, i.e., six lenses enables low cost and reduction in thetotal length in the direction of the optical axis to be achieved. Inaddition, as the aperture stop St is disposed more toward the objectside than the image-side surface of the fourth lens L4, reducing thediameter of each lens will be facilitated. Further, an imaging lens thathas high optical performance, by which back focus can be secured,various aberrations can be favorably corrected and fine images can beobtained through the peripheral portions of the imaging area, can berealized.

Next, preferable configurations of the imaging lenses according to thefirst through third embodiments above of the present invention and theadvantageous effects thereof will be described. Note that preferably,the imaging lens may have any one of the configurations below, or mayhave an arbitrary combination of two or more of the configurations.

It is preferable for conditional formula (4) below to be satisfied:

f56/f<−6.4  (4), where

f: the focal length of the entire system, andf56: the combined focal length of the fifth lens L5 and the sixth lensL6.

Satisfying the upper limit defined by conditional formula (4)facilitates preventing the combined power of the fifth lens L5 and thesixth lens L6, which is negative, from becoming too strong. Thereby,correcting field curvature will be facilitated and suppressing theangles at which the rays enter the image sensor will be facilitated aswell. Further, as suppressing the combined power of the fifth lens L5and the sixth lens L6 becomes easy, suppressing focus shift caused bychanges in temperature will be facilitated in the case that the fifthlens L5 and the sixth lens L6 are made of plastics.

It is preferable for conditional formula (5) below to be satisfied:

f34/f56<0.0  (5), where

f34: the combined focal length of the third lens L3 and the fourth lensL4, andf56: the combined focal length of the fifth lens L5 and the sixth lensL6.

Satisfying the upper limit defined by conditional formula (5) makes thevalue of conditional formula (5) negative. Therefore, one of f34 and f56can be made positive and the other can be made negative. Accordingly,focus shift caused by changes in temperature can be easily suppressed bythe positive and negative powers cancelling each other out when thetemperature changes.

It is preferable for both conditional formula (5) and conditionalformula (6) below to be satisfied:

0.0<f34/f  (6).

Satisfying conditional formula (6) enables the value of f34 to be madepositive. Satisfying the upper limit defined by conditional formula (5)and conditional formula (6) at the same time enables the values of f34and f56 to be positive and negative in respective and enables focusshift due to changes in the temperature to be suppressed.

It is preferable for the materials of the third lens L3, the fourth lensL4, the fifth lens L5 and the sixth lens L6 to be plastic. This enablesthe lens to be configured at low cost.

It is preferable for conditional formula (7) below to be satisfied:

2.0<f3456/f  (7), where

f3456: the combined focal length of the third lens L3, the fourth lensL4, the fifth lensL5 and the sixth lens L6.

Satisfying the lower limit defined by conditional formula (7)facilitates preventing the combined power of the third lens L3 throughthe sixth lens L6 from becoming too strong as a positive power andfacilitates securing back focus.

Further, it is preferable for the materials of the third lens L3, thefourth lens L4, the fifth lens L15 and the sixth lens L6 to be plasticand for conditional formula (7) above to be satisfied. This facilitatespreventing the combined focal length of the plastic lenses from becomingtoo strong as a positive power and facilitates suppressing focus shift.

It is preferable for conditional formula (8) below to be satisfied:

0.9<νd2/νd3  (8), where

νd2: the Abbe number of the material of the second lens L2 with respectto the d-line, andνd3: the Abbe number of the material of the third lens L3 with respectto the d-line.

Decreasing the Abbe number of the third lens L3 will be advantageousfrom the viewpoint of correcting longitudinal chromatic aberration.Satisfying the lower limit defined by conditional formula (8)facilitates balancing the ratios of the Abbe number of of the materialsof the second lens L2 and the third lens L3 and facilitates correctingchromatic aberration.

It is preferable for conditional formula (9) to be satisfied:

−2.5<f3/f<−0.5  (9), where

f: the focal length of the entire system, andf3: the focal length of the third lens L3.

Satisfying the lower limit defined by conditional formula (9)facilitates increasing the power of the third lens L3, therebyfacilitating reducing longitudinal chromatic aberration. Satisfying theupper limit defined by conditional formula (9) facilitates suppressingthe error sensitivity of the third lens L3, thereby facilitatingmanufacturing a lens which is resistant to axial displacement and thelike.

It is preferable for the aperture stop St to be provided more toward theobject side than the image-side surface of the fourth lens L4. Disposingthe aperture stop St more toward the object side than the fourth lens L4facilitates reducing the diameters of the lenses. It is preferable forthe aperture stop St to be disposed between the first lens L1 and thesecond lens L2. This facilitates miniaturization of the first lens L1.For example, when the imaging lens is used as a vehicle mounted camera,there is demand for a lens surface which is exposed outside to be madesmall so as to improve the appearance of the car. Disposing the aperturestop St between the first lens L1 and the second lens L2 enables thelens which is exposed outside to be reduced in the size and facilitatesimproving the appearance of the car.

It is preferable for the aperture stop St to be disposed between thesecond lens L2 and the third lens L3 or between the third lens L3 andthe fourth lens L4. This improves balance of the diameters of the lensesat the front and back of the aperture stop St and facilitatessuppressing the maximum diameters of the lenses, resulting infacilitating miniaturization of the lens. Further, disposing theaperture stop St between the second lens L2 and the third lens L3facilitates suppressing the angles at which the rays enter the imagesensor while keeping a good balance of the diameters of the lenses atthe front and back of the aperture stop St, resulting in facilitatingsuppressing the occurrence of shading.

It is preferable for conditional formula (10) below to be satisfied:

−3.0<f3/f4<−0.2  (10), where

f3: the focal length of the third lens L3, andf4: the focal length of the fourth lens L4.

Satisfying the upper and lower limits defined by conditional formula(10) can make good power balance between the third lens L3 and thefourth lens L4, thereby facilitating correction of chromatic aberration.Satisfying the upper limit defined by conditional formula (10) canprevents the power of the third lens L3 from becoming too strong,resulting in correction of field curvature being facilitated, or canprevents the power of the fourth lens L4 from becoming too weak,resulting in correction of spherical aberration and field curvaturebeing facilitated. Satisfying the lower limit defined by conditionalformula (10) can prevent the power of the third lens L3 from becomingtoo weak, resulting in correction of longitudinal chromatic aberrationbeing facilitated, or can prevent the power of the fourth lens L4 frombecoming too strong, resulting in correction of spherical aberration andsecuring of back focus being facilitated.

It is preferable for conditional formula (11) below to be satisfied:

0.2<f12/f<5.0  (11), where

f: the focal length of the entire system, andf12: the combined focal length of the first lens L1 and the second lensL2.

Satisfying the upper limit defined by conditional formula (11)facilitates increasing the combined power of the first lens L1 and thesecond lens L2, resulting in facilitating correction of sphericalaberration and field curvature. Satisfying the lower limit defined byconditional formula (11) facilitates preventing the combined power ofthe first lens L1 and the second lens L2 from becoming too strong as apositive power, resulting in correction of field curvature beingfacilitated.

It is preferable for three or less of the refractive indices among therefractive indices Nd1 through Nd6 of the materials of the first lens L1through the sixth lens L6 with respect to the d-line to exceed 1.8. Arefractive index exceeding 1.8 will increase the cost for the materialof the lens. Therefore, it is preferable for the number of therefractive indices which exceed 1.8 to be three or less, even morepreferably two or less and still more preferably one or less.

It is preferable for conditional formula (12) below to be satisfied:

(Nd1+Nd2+Nd3+Nd4+Nd5+Nd6)/6<1.70  (12), where

Nd1 through Nd6: the refractive indices of the materials of the firstlens L1 through the sixth lens L6 with respect to the d-line.

Satisfying the upper limit defined by conditional formula (12)facilitates suppressing the refractive index of each lens, resulting inreduction of the cost for the material being facilitated.

It is preferable for the number of the refractive indices which exceed1.8 among the refractive indices Nd1 through Nd6 of the materials of thefirst lens L1 through the sixth lens L6 with respect to the d-line to bethree or less, and for conditional formula (12) to be satisfied. Thisfacilitates suppressing the refractive index of each lens, therebyfacilitating the reduction in the cost for the material.

It is preferable for conditional formula (13) below to be satisfied:

2.0<L/f<7.0  (13), where

L: the distance from the object-side surface of the first lens L1 to theimaging plane (back focus corresponds to the air converted length), andf: the focal length of the entire system.

Setting the value of L/f to exceed the upper limit defined byconditional formula (13) will increase the total length of the lens,resulting in miniaturization becoming difficult. Setting the value ofL/f to fall below the lower limit defined by conditional formula (13)will make it difficult to widen the angle of view or will make the totallength too short, thereby each lens becoming thin. As the result,manufacturing the lens will be difficult or the cost will increase.

It is preferable for conditional formula (14) below to be satisfied:

0.3<Bf/f<1.5  (14), where

Bf: the distance from the image-side surface of the sixth lens L6 to theimaging plane (the air converted length), andf: the focal length of the entire system.

Setting the value of Bf/f to exceed the upper limit defined byconditional formula (14) will increase the amount of back focus,resulting in the size of the lens system being increased. Setting thevalue of Bf/f to fall below the lower limit defined by conditionalformula (14) will make back focus too short, resulting in making itdifficult to dispose various types of filters, a cover glass, or thelike between the lens system and the image sensor.

Note that regarding the distance L from the object-side surface of thefirst lens L1 to the imaging plane along the optical axis and thedistance Bf from the image-side surface of the most-image-side lens (thesixth lens L6) to the imaging plane along the optical axis, an airconverted length will be applied for the distance between themost-image-side lens and the imaging plane (in the case that a coverglass or various types of filters are disposed therebetween, the lengthcorresponding thereto will be calculated in terms of an air convertedlength).

It is preferable for conditional formula (15) below to be satisfied:

45.0<(νd2+νd4+νd5)/3  (15), where

νd2: the Abbe number of the material of the second lens L2 with respectto the d-line,νd4: the Abbe number of the material of the fourth lens L4 with respectto the d-line, andνd5: the Abbe number of the material of the fifth lens L5 with respectto the d-line.

Satisfying the lower limit defined by conditional formula (15)facilitates increasing the Abbe number of each lens, therebyfacilitating correction of longitudinal chromatic aberration and lateralchromatic aberration.

Note that it is preferable for the conditional formulas below, in whichupper limits are added to the conditional formulas above or the lower orupper limits are changed in the conditional formulas above to be furthersatisfied so as to improve the above advantageous effects. In addition,preferably, the conditional formulas to be described below, each ofwhich is configured by combining a changed value of the lower limit anda changed value of the upper limit, may be satisfied. Preferredmodifications of conditional formulas will be described below as anexample, but the modifications of conditional formulas are not limitedto those listed below and the changed values described below may becombined.

It is preferable for conditional formula (1) to be provided with anupper limit, and for the upper limit defined by conditional formula (1)to be 30.0. This facilitates preventing the power of the fifth lens L5from becoming too weak, thereby facilitating correction of sphericalaberration. Further, it is preferable for the upper limit defined byconditional formula (1) to be 20.0, more preferably 17.0, and even morepreferably 8.0 in order to further facilitate correction of sphericalaberration. It is preferable for the lower limit defined by conditionalformula (1) to be 2.5, more preferably 3.0, and even more preferably3.2. As described above, it is more preferable for conditional formulas(1-1) through (1-3) below to be satisfied, for example:

2.5<f5/f<20.0  (1-1)

3.0<f5/f<17.0  (1-2)

3.2<f5/f<17.0  (1-3).

It is preferable for the upper limit defined by conditional formula (2)to be −1.0. This further facilitates increasing the power of the firstlens L1, and facilitates securing back focus and reducing the size ofthe lens system in the radial direction. Note that it is preferable forthe upper limit defined by conditional formula (2) to be −2.0, and morepreferably −2.5. Further, it is preferable for the lower limit definedby conditional formula (2) to be −3.9, more preferably −3.8, and evenmore preferably −3.7. As described above, it is more preferable forconditional formulas (2-1) through (2-3) below to be satisfied, forexample:

−3.9<R1/f<−1.0  (2-1)

−3.9<R1/f<−2.0  (2-2)

−3.8<R1/f<−2.5  (2-3).

It is preferable for the upper limit defined by conditional formula (3)to be 0.40, more preferably 0.35, and even more preferably 0.30.Further, it is preferable for the lower limit defined by conditionalformula (3) to be 0.02. This facilitates suppressing the power of thefourth lens L4 or preventing the power of the fifth lens L5 fromexcessively decreasing, resulting in correction of spherical aberrationbeing facilitated. Note that it is more preferable for the lower limitdefined by conditional formula (3) to be 0.05. As described above, it ismore preferable for conditional formulas (3-1) through (3-3) below to besatisfied, for example:

0.02<f4/f5<0.40  (3-1)

0.02<f4/f5<0.35  (3-2)

0.05<f4/f5<0.35  (3-3).

It is preferable for the upper limit defined by conditional formula (4)to be −7.0, more preferably −7.2, and even more preferably −7.5. It ispreferable for conditional formula (4) to be provided with a lower limitand for the lower limit defined by conditional formula (4) to be −100.0.Thereby, correction of field curvature will be facilitated by preventingthe combined power of the fifth lens L5 and the sixth lens L6, which isnegative, from excessively decreasing. Further, it is preferable for thelower limit defined by conditional formula (4) to be −50.0, morepreferably −45.0, and even more preferably −20.0 in order to furtherfacilitate correction of field curvature. As described above, it is morepreferable for conditional formulas (4-1) through (4-3) below to besatisfied, for example:

f56/f<−7.0  (4-1)

f56/f<−7.2  (4-2)

−50.0<f56/f<−7.2  (4-3).

It is preferable for the upper limit defined by conditional formula (5)to be −0.02, more preferably −0.04, and even more preferably −0.06. Inthe case that conditional formula (6) is satisfied, it is preferable forconditional formula (5) to be provided with a lower limit and the lowerlimit defined by conditional formula (5) to be −1.5. This facilitatesincreasing the positive power of f34, thereby further facilitatingsuppressing focus shift and correcting filed curvature. Further, it ispreferable for the lower limit defined by conditional formula (5) to be−1.2, more preferably −1.0, even more preferably −0.9, still morepreferably −0.7, and even still more preferably −0.6 in order tofacilitate suppression of focus shift and correction of field curvature.As described above, it is more preferable for conditional formulas (5-1)through (5-4) below to be satisfied, for example:

−1.5<f34/f56<0.0  (5-1)

−0.9<f34/f56<0.0  (5-2)

−1.2<f34/f56<−0.05  (5-3)

−0.7<f34/f56<−0.02  (5-4)

It is preferable for conditional formula (7) to be provided with anupper limit and for the upper limit defined by conditional formula (7)to be 6.0. This enables the combined power of the third lens L3 throughthe sixth lens L6 to be prevented from excessively decreasing, andfacilitates suppressing the angles at which the rays enter the imagingsurface and correcting field curvature. It is preferable for the upperlimit defined by conditional formula (7) to be 5.0, and more preferably4.0. It is preferable for the lower limit defined by conditional formula(7) to be 2.5, more preferably 2.7, and even more preferably 2.8. Asdescribed above, it is more preferable for conditional formulas (7-1)through (7-3) below to be satisfied, for example:

2.5<f3456/f<6.0  (7-1)

2.5<f3456/f<5.0  (7-2)

2.7<f3456/f<4.0  (7-3).

It is preferable for conditional formula (8) to be provided with anupper limit and for the upper limit defined by conditional formula (8)to be 3.5. This causes the Abbe number of the third lens L3 toexcessively decrease or the Abbe number of the second lens L2 toexcessively increase, resulting in avoiding high cost becoming easy.Further, decreasing the Abbe number of the third lens L3 will cause therefractive index of the third lens L3 to increase and enable the powerof the third lens L3 to be prevented from excessively increasing,resulting in correction of field curvature being facilitated. It ispreferable for the upper limit defined by conditional formula (8) to be3.0, and more preferably 2.5. It is preferable for the lower limitdefined by conditional formula (8) to be 1.0, more preferably 1.2, andeven more preferably 1.5. As described above, it is more preferable forconditional formulas (8-1) through (8-3) below to be satisfied, forexample:

1.0<νd2/νd3<3.5  (8-1)

1.2<νd2/νd3<3.0  (8-2)

1.5<νd2/νd3<2.5  (8-3).

It is preferable for the upper limit defined by conditional formula (9)to be −0.6, more preferably −0.7, and even more preferably −0.8. It ispreferable for the lower limit defined by conditional formula (9) to be−2.2, more preferably −2.0, even more preferably −1.8, and still morepreferably −1.7. As described above, it is more preferable forconditional formulas (9-1) through (9-3) below to be satisfied, forexample:

−2.2<f3/f<−0.6  (9-1)

−2.0<f3/f<−0.7  (9-2)

−1.8<f3/f<−0.8  (9-3).

It is preferable for the upper limit defined by conditional formula (10)to be −0.5, more preferably −0.7, and even more preferably −0.8. It ispreferable for the lower limit defined by conditional formula (10) to be−2.5, more preferably −2.0, even more preferably −1.8, and still morepreferably −1.7. As described above, it is more preferable forconditional formulas (10-1) through (10-3) below to be satisfied, forexample:

−2.5<f3/f4<−0.5  (10-1)

−2.0<f3/f4<−0.7  (10-2)

−1.8<f3/f4<−0.8  (10-3).

It is preferable for the upper limit defined by conditional formula (11)to be 4.0, more preferably 3.0, and even more preferably 2.0. It ispreferable for the lower limit defined by conditional formula (11) to be0.5, more preferably 0.8, and even more preferably 1.0. As describedabove, it is more preferable for conditional formulas (11-1) through(11-3) below to be satisfied, for example:

0.5<f12/f<4.0  (11-1)

0.8<f12/f<3.0  (11-2)

1.0<f12/f<2.0  (11-3).

It is preferable for the upper limit defined by conditional formula (12)to be 1.68, and more preferably 1.64. It is preferable for conditionalformula (12) to be provided with a lower limit and for the lower limitdefined by conditional formula (12) to be 1.50. This enables therefractive indices of the materials of the first lens L1 through thesixth lens L6 with respect to the d-line to be prevented fromexcessively decreasing and facilitates increasing the power of eachlens, thereby facilitating miniaturization of the lens system. It ispreferable for the lower limit defined by conditional formula (12) to be1.55, and more preferably 1.57. As described above, it is morepreferable for conditional formulas (12-1) through (12-3) below to besatisfied, for example:

1.50<(Nd1+Nd2+Nd3+Nd4+Nd5+Nd6)/6<1.70  (12-1)

1.55<(Nd1+Nd2+Nd3+Nd4+Nd5+Nd6)/6<1.68  (12-2)

1.57<(Nd1+Nd2+Nd3+Nd4+Nd5+Nd6)/6<1.64  (12-3).

It is preferable for the upper limit defined by conditional formula (13)to be 6.0, more preferably 5.0, and even more preferably 4.5. It ispreferable for the lower limit defined by conditional formula (13) to be2.5, more preferably 2.8, and even more preferably 3.0. As describedabove, it is more preferable for conditional formulas (13-1) through(13-3) below to be satisfied, for example:

2.5<L/f<6.0  (13-1)

2.8<L/f<5.0  (13-2)

3.0<L/f<4.5  (13-3).

It is preferable for the lower limit defined by conditional formula (14)to be 0.5, more preferably 0.6, and even more preferably 0.65. It ispreferable for the upper limit defined by conditional formula (14) to be1.2, more preferably 1.0, and even more preferably 0.9. As describedabove, it is more preferable for conditional formulas (14-1) through(14-3) below to be satisfied, for example:

0.5<Bf/f<1.5  (14-1)

0.6<Bf/f<1.2  (14-2)

0.6<Bf/f<1.0  (14-3).

It is preferable for conditional formula (15) to be provided with anupper limit and for the upper limit to be 60.0. Thereby, preventing theAbbe numbers of the materials of the second lens L2, the fourth lens L4,and the fifth lens L5 with respect to the d-line from excessivelyincreasing facilitates increase of the refractive indices of thematerials and further increasing the power of each lens facilitatesreduction of the diameters of the lenses. Further, it will be easy toprevent the cost for the glass materials from increasing due to anexcessive increase in the Abbe numbers of the materials. It ispreferable for the upper limit defined by conditional formula (15) to be58.0, and more preferably 56.0. It is preferable for the lower limitdefined by conditional formula (15) to be 47.0, more preferably 49.0,even more preferably 50.0, and still more preferably 51.0. As describedabove, it is more preferable for conditional formulas (15-1) through(15-3) below to be satisfied, for example:

47.0<(νd2+νd4+νd5)/3  (15-1)

49.0<(νd2+νd4+νd5)/3<60.0  (15-2)

51.0<(νd2+νd4+νd5)/3<58.0  (15-3).

It is preferable for the Abbe number of the material of the first lensL1 with respect to the d-line to be greater than or equal to 40. Thisenables longitudinal chromatic aberration and lateral chromaticaberration to be corrected favorably. Further, it is more preferable forthe Abbe number of the material of the first lens L1 with respect to thed-line to be greater than or equal to 50, and even more preferablygreater than or equal to 55.

It is preferable for the Abbe number of the material of the second lensL2 with respect to the d-line to be greater than or equal to 25. Thisenables longitudinal chromatic aberration to be corrected favorably.Further, it is more preferable for the Abbe number of the material ofthe second lens L2 with respect to the d-line to be greater than orequal to 35, and even more preferably greater than or equal to 40.

It is preferable for the Abbe number of the material of the third lensL3 with respect to the d-line to be less than or equal to 35. Thisenables longitudinal chromatic aberration to be corrected favorably.Further, it is more preferable for the Abbe number of the material ofthe third lens L3 with respect to the d-line to be less than or equal to30, even more preferably less than or equal to 28, and still morepreferably less than or equal to 26.

It is preferable for the Abbe number of the material of the fourth lensL4 with respect to the d-line to be greater than or equal to 40. Thisenables longitudinal chromatic aberration and lateral chromaticaberration to be corrected favorably. Further, it is more preferable forthe Abbe number of the material of the fourth lens L4 with respect tothe d-line to be greater than or equal to 50, and even more preferablygreater than or equal to 55.

It is preferable for the the Abbe number of the material of the fifthlens L5 with respect to the d-line to be greater than or equal to 40.This enables longitudinal chromatic aberration and lateral chromaticaberration to be corrected favorably. Further, it is more preferable forthe Abbe number of the material of the fifth lens L5 with respect to thed-line to be greater than or equal to 50, and even more preferablygreater than or equal to 52.

It is preferable for the Abbe number of the material of the sixth lensL6 with respect to the d-line to be less than or equal to 32. Thisenables lateral chromatic aberration to be corrected favorably. Further,it is more preferable for the Abbe number of the material of the sixthlens L6 with respect to the d-line to be less than or equal to 26, andeven more preferably less than or equal to 25.

It is preferable for at least one side surface of the fourth lens L4 tobe aspherical. Configuring at least one side surface of the fourth lensL4 to be aspherical facilitates correction of field curvature andspherical aberration, resulting in enabling favorable resolution to beobtained. It is more preferable for both surfaces of the fourth lens L4to be aspherical.

It is preferable for the object-side surface of the fourth lens L4 to beaspherical. It is preferable for the object-side surface of the fourthlens L4 to have a shape in which both of the center and the edge of theeffective diameter have positive powers and the positive power at theedge of the effective diameter is weaker than that of the center.Configuring the fourth lens L4 to have such a shape facilitatescorrection of spherical aberration and field curvature.

Note that “the effective diameter of a surface” refers to the diameterof a circle constituted by an outermost point in the radial direction (apoint farthest from the optical axis) among points where all of the rayscontributing to image formation intersect with lens surfaces, and theterm “edge of the effective diameter” refers to this outermost point.Note that in systems which have rotation symmetry with respect to theoptical axis, a graphic constituted by the above outermost point is acircle. However, in systems which do not have rotation symmetry, thegraphic is not a circle. In such a case, the diameter of an equivalentcircle may be the effective diameter.

Further, regarding a shape of an aspherical surface, when a certainpoint on a lens surface i (i is a symbol which represents thecorresponding lens surface. For example, when the object-side surface ofthe fourth lens L4 is represented by 8, the following description withrespect to the object-side surface of the fourth lens L4 can beunderstood with i as 8.) of each lens is designated as Xi and anintersection of the normal line on the point and the optical axis isdesignated as Pi; the length (|Xi-Pi|) of Xi-Pi is defined as theabsolute value |RXi| of the radius of curvature on the point Xi and Piis defined as the center of curvature at the point Xi. Further, anintersection of the i-th lens surface and the optical axis is designatedas Qi. In this case, a power at a point Xi is defined depending onwhether a point Pi is on the object side or the image side based on apoint Qi as the reference. In the object-side surface, in the case thata point Pi is toward the image side than a point Qi, the power isdefined as positive, whereas in the case that the point Pi is toward theobject side than the Qi, the power is defined as negative. In theimage-side surface, in the case that the point Pi is toward the objectside than the point Qi, the power is defined as positive, whereas in thecase that the point Pi is toward the image side than the point Qi, thepower is defined as negative.

When the power in the center is compared to the power at the point Xi,the absolute value of the radius of curvature in the center (paraxialradius of curvature) is compared to the absolute value |RXi| of theradius of curvature at the point Xi. In the case that |RXi| is smallerthan the absolute value of the paraxial radius of curvature, the powerat the point Xi is greater than the power in the center. In contrast, inthe case that |RXi| is greater than the absolute value of the paraxialradius of curvature, the power at the point Xi is weaker than the powerin the center. The same applies to both the case that a surface has thepositive power and the case that a surface has the negative power.

Here, referring to FIG. 2, the shape of the object-side surface of thefourth lens L4 above will be described. FIG. 2 illustrates an opticalpath diagram of the imaging lens 1 shown in FIG. 1. In FIG. 2, a pointQ8 is the center of the object-side surface of the fourth lens L4 and anintersection of the object-side surface of the fourth lens L4 and theoptical axis Z. Further, in FIG. 2, the point X8 on the object-sidesurface of the fourth lens L4 is at the edge of the effective diameter,and is an intersection of the outermost ray 6, which is included inoff-axis rays 3, and the object-side surface of the fourth lens L4. InFIG. 2, although the point X8 is at the edge of the effective diameter,the same applies to other points because the point X8 is an arbitrarypoint on the object-side surface of the fourth lens L4.

In this case, an intersection of the normal line at a point X8 on thelens surface and the optical axis Z is defined as a point P8 as shown inFIG. 2, a line segment X8-P8 connecting between a point X8 and a pointP8 is defined as the radius of curvature RX8 at the point X8, and thelength |X8-P8| of the line segment X8-P8 is defined as the absolutevalue |RX8| of the radius of curvature RX8. That is, |X8-P8| is |RX8|.Further, the radius of curvature at the point Q8, i.e., the radius ofcurvature in the center of the object-side surface of the fourth lens L4is designated as R8, and the absolute value thereof is designated as|R8| (not shown in FIG. 2).

The expression “a shape in which both of the center and the edge of theeffective diameter have positive powers and the positive power at theedge of the effective diameter is weaker than that of the center” of thethe object-side surface of the fourth lens L4 refers to, when a point X8is the edge of the effective diameter, a convex shape in a paraxialregion including a point Q8 and a shape in which a point P8 is moretoward the image side than the point Q8 and the absolute value |RX8| ofthe radius of curvature at a point X8 is greater than the absolute value|R8| of the radius of curvature at the point Q8.

It is preferable for at least one side surface of the fifth lens L5 tobe an aspherical surface. Configuring at least one side surface of thefifth lens L5 to be an aspherical surface facilitates correction offield curvature and spherical aberration, thereby enabling favorableresolution to be obtained. It is more preferable for both side surfacesof the fifth lens L5 to be aspherical.

It is preferable for the object-side surface of the fifth lens L5 to bean aspherical surface. It is preferable for the object-side surface ofthe fifth lens L5 to have a shape in which both of the center and theedge of the effective diameter have positive powers and in which thepositive power at the edge of the effective diameter is greater thanthat of the center. Alternatively, it is preferable for the object-sidesurface of the fifth lens L5 to have a shape in which the center has anegative power and the edge of the effective diameter has a positivepower. Configuring the fifth lens L5 to have such a shape facilitatescorrection of field curvature.

The above shape of the object-side surface of the fifth lens L5 can beunderstood as described below in the same manner as in the shape of theobject-side surface of the fourth lens L4 which was described by usingFIG. 2. In a cross section of the lens, when a point on the object-sidesurface of the fifth lens L5 is X10 and the intersection of the normalline at the point and the optical axis Z is a point P10; a line segmentX10-P10 connecting between the point X10 and the point P10 is the radiusof curvature at the point X10, the length |X10-P10| of the line segmentconnecting between the point X10 and the point P10 is the absolute value|RX10| of the radius of curvature at the point X10. That is, |X10-P10|is |RX10|. Further, the intersection of the object-side surface of thefifth lens L5 and the optical axis Z, i.e., the center of theobject-side surface of the fifth lens L5 is a point Q10. The absolutevalue of the radius of curvature at the point Q10 is |R10|.

The expression “a shape in which both of the center and the edge of theeffective diameter have positive powers and in which the positive powerat the edge of the effective diameter is greater than that of thecenter” of the the object-side surface of the fifth lens L5 refers to,when a point X10 is the edge of the effective diameter, a convex shapein the paraxial region including a point Q10 and a shape in which apoint P10 is more toward the image side than the point Q10 and theabsolute value |RX10| of the radius of curvature at a point X10 issmaller than the absolute value |R10| of the radius of curvature at thepoint Q10.

The expression “a shape in which the center has a negative power and theedge of the effective diameter has a positive power” of the object-sidesurface of the fifth lens L5 refers to, when a X10 is the edge of theeffective diameter, a concave shape in the paraxial region including apoint Q10 and a shape in which a point P10 is more toward the image sidethan the point Q10.

It is preferable for the image-side surface of the fifth lens L5 to bean aspherical surface. It is preferable for the image-side surface ofthe fifth lens L5 to have a shape in which both of the center and theedge of the effective diameter have positive powers and the positivepower at the edge of the effective diameter is weaker than tha of thecenter. Configuring the fifth lens L5 to have such a shape facilitatescorrection of field curvature.

The above shape of the image-side surface of the fifth lens L5 can beunderstood as described below in the same manner as in the shape of theobject-side surface of the fourth lens L4 which was described by usingFIG. 2. In a cross section of the lens, when a point on the image-sidesurface of the fifth lens L5 is X11 and the intersection of the normalline at the point and the optical axis Z is a point P11; a line segmentX11-P11 connecting between the point X11 and the point P11 is the radiusof curvature at the point X11, the length |X11-P11| of the line segmentconnecting between the point X11 and the point P11 is the absolute value|RX11| of the radius of curvature at the point X11. That is, |X11-P11|is |RX11|. Further, the intersection of the image-side surface of thefifth lens L5 and the optical axis Z, i.e., the center of the image-sidesurface of the fifth lens L5 is a point Q11. The absolute value of theradius of curvature at the point Q11 is |R11|.

The expression “a shape in which both of the center and the edge of theeffective diameter have positive powers and in which the positive powerat the edge of the effective diameter is weaker than that of the center”of the the image-side surface of the fifth lens L5 refers to, when apoint X11 is the edge of the effective diameter, a convex shape in theparaxial region including a point Q11 and a shape in which a point P11is more toward the object side than the point Q11 and the absolute value|RX11| of the radius of curvature at a point X11 is greater than theabsolute value |R11| of the radius of curvature at the point Q11.

It is preferable for at least one side surface of the sixth lens L6 tobe an aspherical surface. Configuring at least one side surface of thesixth lens L6 to be an aspherical surface facilitates correction offield curvature and spherical aberration, thereby enabling favorableresolution to be obtained. It is more preferable for both side surfacesof the sixth lens L6 to be aspherical.

It is preferable for the object-side surface of the sixth lens L6 to bean aspherical surface. It is preferable for the object-side surface ofthe sixth lens L6 to have a shape in which both of the center and theedge of the effective diameter have negative powers and the negativepower at the edge of the effective diameter is greater than that of thecenter. Configuring the sixth lens L6 to have such a shape facilitatescorrection of field curvature.

The above shape of the object-side surface of the sixth lens L6 can beunderstood as described below in the same manner as in the shape of theobject-side surface of the fourth lens L4 which was described by usingFIG. 2. In a cross section of the lens, when a point on the object-sidesurface of the sixth lens L6 is X12 and the intersection of the normalline at the point and the optical axis Z is a point P12; a line segmentX12-P12 connecting between the point X12 and the point P12 is the radiusof curvature at the point X12, the length |X12-P12| of the line segmentconnecting between the point X12 and the point P12 is the absolute value|RX12| of the radius of curvature at the point X12. That is, |X12-P12|is |RX12|. Further, the intersection of the object-side surface of thesixth lens L6 and the optical axis Z, i.e., the center of theobject-side surface of the sixth lens L6 is a point Q12. The absolutevalue of the radius of curvature at the point Q12 is |R12|.

The expression “a shape in which both of the center and the edge of theeffective diameter have negative powes and in which the negative powerat the edge of the effective diameter is greater than that of thecenter” of the the object-side surface of the sixth lens L6 refers to,when a point X12 is the edge of the effective diameter, a concave shapein the paraxial region including a point Q12 and a shape in which apoint P12 is more toward the object side than the point Q12 and theabsolute value |RX12| of the radius of curvature at a point X12 issmaller than the absolute value |R12| of the radius of curvature at thepoint Q12.

It is preferable for at least one side surface of the third lens L3 tobe an aspherical surface. Configuring at least one side surface of thethird lens L3 to be an aspherical surface facilitates correction offield curvature and spherical aberration, thereby enabling favorableresolution to be obtained. It is more preferable for both side surfacesof the third lens L3 to be aspherical.

It is preferable for the object-side surface of the third lens L3 to bean aspherical surface. It is preferable for the object-side surface ofthe third lens L3 to have a shape in which both of the center and theedge of the effective diameter have negative powers and the negativepower at the edge of the effective diameter is weaker than that of thecenter. Configuring the object-side surface of the third lens L3 to havesuch a shape facilitates correction of field curvature.

The above shape of the object-side surface of the third lens L3 can beunderstood as described below in the same manner as in the shape of theobject-side surface of the fourth lens L4 which was described by usingFIG. 2. In a cross section of the lens, when a point on the object-sidesurface of the third lens L3 is X6 and the intersection of the normalline at the point and the optical axis Z is a point P6; a line segmentX6-P6 connecting between the point X6 and the point P6 is the radius ofcurvature at the point X6, the length |X6-P6| of the line segmentconnecting between the point X6 and the point P6 is the absolute value|RX6| of the radius of curvature at the point X6. That is, |X6-P6| is|RX6|. Further, the intersection of the object-side surface of the thirdlens L3 and the optical axis Z, i.e., the center of the object-sidesurface of the third lens L3 is a point Q6. The absolute value of theradius of curvature at the point Q6 is |R6|.

The expression “a shape in which both of the center and the edge of theeffective diameter have negative powers and in which the negative powerat the edge of the effective diameter is weaker than that of the center”of the the object-side surface of the third lens L3 refers to, when apoint X6 is the edge of the effective diameter, a concave shape in theparaxial region including a point Q6 and a shape in which a point P6 ismore toward the object side than the point Q6 and the absolute value|RX6| of the radius of curvature at a point X6 is greater than theabsolute value |R6| of the radius of curvature at the point Q6.

It is preferable for the image-side surface of the third lens L3 to bean aspherical surface. It is preferable for the image-side surface ofthe third lens L3 to have a shape in which both of the center and theedge of the effective diameter have negative powers and in which thenegative power at the edge of the effective diameter is greater thanthat of the center. Configuring the third lens L3 to have such a shapefacilitates correction of chromatic aberration.

The above shape of the image-side surface of the third lens L3 can beunderstood as described below in the same manner as in the shape of theobject-side surface of the fourth lens L4 which was described by usingFIG. 2. In a cross section of the lens, when a point on the image-sidesurface of the third lens L3 is X7 and the intersection of the normalline at the point and the optical axis Z is a point P7; a line segmentX7-P7 connecting between the point X7 and the point P7 is the radius ofcurvature at the point X7, the length |X7-P7| of the line segmentconnecting between the point X7 and the point P7 is the absolute value|RX7| of the radius of curvature at the point X7. That is, |X7-P7| is|RX7|. Further, the intersection of the image-side surface of the thirdlens L3 and the optical axis Z, i.e., the center of the image-sidesurface of the third lens L3 is a point Q7. The absolute value of theradius of curvature at the point Q7 is |R7|.

The expression “a shape in which both of the center and the edge of theeffective diameter have negative powers and in which the negative powerat the edge of the effective diameter is greater than that of thecenter” of the the image-side surface of the third lens L3 refers to,when a point X7 is the edge of the effective diameter, a concave shapein the paraxial region including a point Q7 and a shape in which a pointP7 is more toward the image side than the point Q7 and the absolutevalue |RX7| of the radius of curvature at a point X7 is smaller than theabsolute value |R7| of the radius of curvature at the point Q7.

The image-side surface of the third lens L3 may have a shape in whichboth of the center and the edge of the effective diameter have negativepowers and in which the negative power at the edge of the effectivediameter is weaker than that of the center. Configuring the third lensL3 to have such a shape facilitates correction of field curvature.

The expression “a shape in which both of the center and the edge of theeffective diameter have negative powers and in which the negative powerat the edge of the effective diameter is weaker than that of the center”of the the image-side surface of the third lens L3 refers to, when apoint X7 is the edge of the effective diameter, a concave shape in theparaxial region including a point Q7 and a shape in which a point P7 ismore toward the image side than the point Q7 and the absolute value|RX7| of the radius of curvature at a point X7 is greater than theabsolute value |R7| of the radius of curvature at the point Q7.

It is preferable for the first lens L1 to be a biconcave lens. Thisenables the negative power of the first lens L1 to increase, which isadvantageous from the viewpoint of widening the angle of view and whichfacilitates securing a long back focus.

It is preferable for the second lens L2 to be a biconvex lens. Thisenables the power of the second lens L2 to increase and the combinedpowers of the first lens L1 and the second lens L2 to be well balancedeven in the case that the power of the first lens L1 is caused to beincreased. Thereby, correction of comatic aberration and field curvaturewill be facilitated.

It is preferable for the third lens L3 to be a biconcave lens. Thisenables the power of the third lens L3 to increase, thereby facilitatingcorrection of longitudinal chromatic aberration and lateral chromaticaberration.

It is preferable for the fourth lens L4 to be a biconvex lens. Thisenables the power of the fourth lens L4 to increase, therebyfacilitating correction of chromatic aberration between the fourth lensL4 and the third lens L3.

It is preferable for the fifth lens L5 to have a convex surface towardthe image side. This facilitates correction of field curvature.

The fifth lens L5 may be a biconvex lens. This facilitates increasingthe power of the fifth lens L5, thereby facilitating correction ofspherical aberration.

The fifth lens L5 may be a meniscus lens with a convex surface towardthe image side. This facilitates correction of field curvature.

It is preferable for the sixth lens L6 to be a lens with a concavesurface toward the object side. This facilitates increasing the power ofthe sixth lens L6, thereby facilitating correction of chromaticaberration between the sixth lens L6 and the fifth lens L5.

It is preferable for the sixth lens L6 to be a meniscus lens with aconcave surface toward the object side or to be a plano-concave lenswith a concave surface toward the object side. This enables lateralchromatic aberration and field curvature to be corrected favorably.Telecentricity can be improved compared to the case that the sixth lensL6 is a biconcave lens.

It is preferable for the object-side surface of the first lens L1 tohave a concave surface toward the object side. This facilitatesincreasing the power of the first lens L1, which is advantageous fromthe viewpoint of widening the angle of view, and facilitates reducingthe diameter of the first lens L1, which is advantageous from theviewpoint of miniaturization.

It is preferable for the image-side surface of the first lens L1 to be aconcave surface. This facilitates increasing the power of the first lensL1, which is advantageous from the viewpoint of widening the angle ofview.

It is preferable for the object-side surface of the second lens L2 to bea convex surface. This facilitates increasing the power of the secondlens L2, thereby facilitating correction of field curvature.

It is preferable for the image-side surface of the second lens L2 to bea convex surface. This facilitates increasing the power of the secondlens L2, thereby facilitating correction of field curvature.

It is preferable for the object-side surface of the third lens L3 to bea concave surface. This facilitates increasing the power of the thirdlens L3, thereby facilitating correction of longitudinal chromaticaberration.

It is preferable for the image-side surface of the third lens L3 to be aconcave surface. This facilitates increasing the power of the third lensL3, thereby facilitating correction of longitudinal chromaticaberration.

It is preferable for the object-side surface of the fourth lens L4 to bea convex surface. This facilitates increasing the power of the fourthlens L4, thereby facilitating correction of longitudinal chromaticaberration.

It is preferable for the image-side surface of the fourth lens L4 to bea convex surface. This facilitates increasing the power of the fourthlens L4, thereby facilitating correction of longitudinal chromaticaberration.

It is preferable for the object-side surface of the fifth lens L5 to bea convex surface. This facilitates correction of spherical aberration.

The object-side surface of the fifth lens L5 may be a concave surface.This facilitates correction of field curvature.

It is preferable for the image-side surface of the fifth lens L5 to be aconvex surface. This facilitates correction of spherical aberration andfield curvature.

It is preferable for the object-side surface of the sixth lens L6 to bea concave surface. This facilitates correction of field curvature andlateral chromatic aberration.

It is preferable for the image-side surface of the sixth lens L6 to be aplanar surface or a convex surface. Configuring the image-side surfaceof the sixth lens L6 to be a planar surface or a convex surfacefacilitates correction of field curvature.

The image-side surface of the sixth lens L6 may be a concave surface.

It is preferable for the material of the first lens L1 to be a glass.For example, when the imaging lens is used in severe environments asvehicle mounted cameras, surveillance cameras, and the like, there isdemand for the first lens L1 disposed on the most-object side to be madeof a material which is resistant to surface deterioration caused by windand rain, changes in temperature due to direct sunlight, and chemicalagents such as oil, a detergent, and the like, i.e., a material whichhas high water resistance, weather resistance, acid resistance, chemicalresistance, and the like. Further, there is demand for the first lens L1to be made of a material which is hard and not likely to break.Configuring the material to be a glass enables these demands to besatisfied. Alternatively, the material for the first lens L1 may be atransparent ceramic.

Note that a protection means for improving the strength, scratchresistance, and chemical resistance may be provided on the object-sidesurface of the first lens L1. In such a case, the material of the firstlens L1 may be plastic. Such protection means may be a hard coat or awater-repelling coat.

It is preferable for all the lenses to be formed of glass in order tomanufacture an optical system which has superior environmentalresistance. When the imaging lens is applied for use as a lens for asurveillance camera or a lens for a vehicle mounted camera, there is apossibility for the imaging lens to be used under various conditionssuch as a wide temperature range from a high temperature to a lowtemperature, high humidity, and the like. Therefore, it is preferablefor all the lenses to be formed of glass in order to manufacture theoptical system which is resistant to these conditions.

It is preferable for the material of the second lens L2 to be a glass.Configuring the second lens L2 to be formed of a glass facilitates usingthe material with high refractive index, thereby facilitating increasein the power of the second lens L2. As the result, correction of fieldcurvature will become easy. Further, when plastics are applied for usein the third lens L3 through the sixth lens L6, employing a glass forthe second lens L2 which is a convex lens facilitate suppressing focusshift due to changes in temperature.

It is preferable for the materials of any one or a plurality ofarbitrary combinations of the third lens L3 through the sixth lens L6 tobe plastic. Configuring the materials to be plastic facilitatesreduction in the cost and the weight of the lens system and enablesaspherical surface shapes to be manufactured accurately andinexpensively, resulting in correction of spherical aberration and fieldcurvature becoming possible.

It is preferable for the imaging lens to include a plastic lens having apositive power and a plastic lens having a negative power in order tomanufacture the lens system which is resistant to changes intemperature. In general, plastic lenses have characteristics which varysignificantly due to changes in temperature, which causes focus shift tooccur. However, configuring the lens system to include the plastic lenshaving a positive power and the plastic lens having a negative powercauses changes in the power to be cancelled out, thereby enablingdeterioration in performance to be minimized.

Accordingly, it is preferable for one of the third lens L3 and the sixthlens L6 and for one of the fourth lens L4 and the fifth lens L5 to beplastic. It is more preferable for all of the third lens L3 through thesixth lens L6 to be plastic lenses from the viewpoint of cost down.

Note that it is preferable for the number of the plastic lenses havingpositive powers and the number of the plastic lenses having negativepowers to agree. This facilitates balancing the positive power with thenegative power of the plastic lenses, thereby making it easy to suppressfocus shift due to the changes in temperature. Note that if the positivepower and the negative power are well balanced, the number of theplastic lenses having positive powers and the number of the negativelenses having negative powers do not have to agree.

All of the four lenses, the third lens L3 through the sixth lens L6 maybe plastic lenses, or only a pair of any of the lenses among theselenses may be plastic lenses. Alternatively, other lenses may be plasticlenses instead of the third lens L3 through the sixth lens L6. Forexample, the second lens L2 may be a plastic lens instead of the fourthlens L4. Further, the first lens L1 may be a plastic lens instead of thesixth lens L6.

Acrylic, a polyolefin-based material, a polycarbonate-based material, anepoxy resin, PET (Polyethylene terephthalate), PES (Poly EtherSulphone), a polycarbonate, and the like can be employed as the materialof the plastic, for example.

It is preferable for the material of the third lens L3 to be apolycarbonate-based material. This enables the Abbe number thereof to bedecreased, thereby facilitating correction of longitudinal chromaticaberration and lateral chromatic aberration.

It is preferable for the material of the fourth lens L4 to be apolyolefin-based material. This enables the Abbe number thereof to beincreased and facilitates suppressing birefringence of the material,resulting in facilitating obtainment of a favorable resolution.

It is preferable for the material of the fifth lens L5 to be apolyolefin-based material. This enables the Abbe number thereof to beincreased and facilitates suppressing birefringence of the material,resulting in facilitating obtainment of a favorable resolution.

It is preferable for the material of the sixth lens L6 to be apolycarbonate-based material. This enables the Abbe number thereof to bedecreased, thereby facilitating correction of longitudinal chromaticaberration and lateral chromatic aberration.

It is preferable for the center thickness of the first lens L1 to begreater than or equal to 0.8 mm. This enables a hard lens to bemanufactured, thereby enabling a lens, which is resistant to variousimpacts, to be manufactured.

Note that a filter which cuts blue light from ultraviolet light or an IR(InfraRed) cutting filter which cuts infrared light may be providedbetween the lens system and the image sensor 5 according to theapplication of the imaging lens 1. A coating which has the samecharacteristics as those of the filters above may be applied onto thelens surface. Alternatively, materials which absorb ultraviolet light,blue light, infrared light, and the like may be applied as the materialsof any of the lenses.

FIG. 1 shows an example in which an optical member PP that presumesvarious types of filters and the like is disposed between the lenssystem and the image sensor 5, but these various types of filters may bedisposed between the respective lenses, instead. Alternatively, acoating, which exhibits the same effects as the various types offilters, may be applied onto the lens surfaces of any of the lensesincluded in the imaging lens.

Note that there is a possibility that the rays which pass the outside ofthe effective diameters between the respective lenses will become straylight and reach the imaging plane, resulting in turning to ghosts.Accordingly, it is preferable for a light cutting means for shieldingthe stray light to be provided as necessary. As this light cuttingmeans, an opaque paint may be applied onto portions of the outside ofthe effective diameters of the lenses, or an opaque plate may beprovided therein, for example. Alternatively, opaque plates may beprovided as the light cutting means on optical paths of the rays whichbecome stray light. Alternatively, something like a hood for shieldingstray light may be disposed more toward the object side than themost-object-side lens. As one example, FIG. 1 shows an example in whichlight cutting means 11, 12 are provided at the exterior of the effectivediameter of the image-side surface of each of the first lens L1 and thethird lens L3. Note that the positions in which the light cutting meansare provided are not limited to the example shown in FIG. 1, and thelight cutting means may be provided on other lenses or between thelenses.

Further, members such as a stop, and the like which shields peripheralrays may be disposed between the respective lenses within a range inwhich no actual problems for the ratio of the amount of peripheral rayswill arise. The peripheral rays are rays which pass through peripheralportions of an entrance pupil in the optical system among the raysemitted from object points outside of the optical axis Z. Disposing themember which shields the peripheral rays in such a manner enables imagequality of the peripheral portions of the image formation region to beimproved. Further, shielding the light which generates ghosts by themember enables ghosts to be reduced.

Further, it is preferable for the lens system to be constituted only bysix lenses which are a first lens L1, a second lens L2, a third lens L3,a fourth lens L4, a fifth lens L5 and the sixth lens L6. Constitutingthe lens system only by six lenses enables the lens system to beproduced at low cost.

The imaging apparatus according to the present embodiment is providedwith the imaging lens according to the present embodiment. Accordingly,the imaging apparatus can be configured in a small size and at low cost,have a sufficient wide angle of view, and obtain favorable images withhigh resolution by using the image sensor.

Note that images captured by the imaging apparatus provided with theimaging lens according to the first embodiment through the thirdembodiment may be displayed on mobile phones. For example, there is acase that the imaging apparatus provided with the imaging lens of thepresent embodiment is mounted on a car as a vehicle mounted camera, thevehicle mounted camera captures images behind and around the car, andthen the captured images is displayed on a display device. In such acase, in the cars mounted with a car navigation system, the capturedimages can be displayed on the display device of the car navigationsystem. However, in the case that the car navigation system is notmounted on the cars, dedicated display devices such as a liquid crystaldisplay, and the like are required to be installed in the cars. However,display devices are expensive. Meanwhile, the recent mobile phones areequipped with display devices having high performance which enablesviewing moving pictures and web sites. Using mobile phones as thedisplay devices intended for vehicle mounted cameras makes itunnecessary to load dedicated display devices on cars which are notequipped with a car navigation system. As the result, vehicle mountedcameras can be mounted on cars at low cost.

Here, the images captured by the vehicle mounted camera may bewire-transmitted to a mobile phone via a cable, and the like or may bewirelessly transmitted to a mobile phone via infrared communication, andthe like. Further, when the car's gear is set to reverse or a turnsignal is activated, the images captured by the vehicle mounted cameramay be automatically displayed on the display device of the mobile phoneby coordinating the operating condition of the mobile phone with that ofthe car.

Note that the display device for displaying images captured by thevehicle mounted camera is not limited to a mobile phone, and may be sucha portable data terminal as a PDA, and the like, a compact personalcomputer, or a laptop car navigation system.

Further, a mobile phone equipped with the imaging lens of the presentinvention may be fixed to a car to be used as a vehicle mounted camera.Recent smart phones have processing capability which is equivalent tothose of PC's. Accordingly, the cameras for the mobile phones can beemployed in the same manner as vehicle mounted cameras, for example byfixing a mobile phone to a dashboard, and the like in the car, anddirecting the camera forward. Note that a function for recognizing whitelines and road signs and giving a caution may be included as anapplication for the smart phone. Further, the mobile phone may be asystem which executes warnings when dozing and looking-aside are foundby directing the camera towards a driver. Further, the mobile phone maybe a part of the system that performs a steering wheel operation bycoordinating with the car. There is demand for vehicle mounted camera tobe resistant to severe environments because cars are left in hightemperature environments and low temperature environments. When theimaging lens of the present invention is mounted on mobile phones, themobile phones will be carried with drivers out of the cars except whiledriving. Accordingly, the imaging lens can be made less resistant to theenvironment; thereby a vehicle mounted system can be introduced at lowcost.

[Numerical Example of the Imaging Lens]

Next, the Numerical Example of the imaging lens of the present inventionwill be described. The cross sectional views of the imaging lenses ofthe Examples 1 through 15 are shown in FIGS. 3 through 17. In FIGS. 3through 17, the left side is the object side, and the right side is theimage side. An aperture stop St, an optical member PP and an imagesensor 5 disposed on an imaging plane Sim are also shown in the samemanner as in FIG. 1. An aperture stop St of each of the Figures does notnecessarily represent the shape or size thereof, but the positionthereof on the optical axis Z. In each Example, symbols Ri, Di (i=1, 2,3, . . . ) of the cross sectional views of the lens respectivelycorrespond to Ri, Di of the lens data to be described below.

Tables 1 through 15 show lens data of the imaging lenses of Examples 1through 15. In each Table, (A) shows basic lens data, (B) shows varioustypes of data, and (C) shows aspherical surface data.

In basic lens data, the column of Si shows the i-th (i=1, 2, 3, . . . )surface number, the value of i sequentially increasing from theobject-side surface of the constituent element at the most object side,which is designated as 1, toward the image side. The column Ri shows theradii of curvature of the i-th surface, and the column Di shows thedistances between i-th surfaces and i+1st surfaces along the opticalaxis Z. Note that the sign of the radius of curvature is positive in thecase that a surface shape has a convex surface toward the object side,and negative in the case that a surface shape has a convex toward theimage side. Further, the column Ndj shows the refractive indices of j-th(j=1, 2, 3, . . . ) optical elements with respect to the d-line(wavelength: 587.6 nm), the value of j sequentially increasing from theconstituent element at the most object side, which is designated as 1,toward the image side. The column νdj shows the Abbe numbers of j-thoptical elements with respect to the d-line (wavelength: 587.6 nm). Notethat the basic lens data also shows the aperture stop St and an opticalmember PP. The column of the surface number of a surface correspondingto the aperture stop St indicates the text (St).

In the basic lens data, the mark “*” is indicated at surface numbers ofaspherical surfaces. Numerical values of paraxial radii of curvature(the radii of curvature of the center) are shown as the radii ofcurvature of aspherical surfaces. The aspherical surface data showssurface numbers of the aspherical surfaces and aspherical surfacecoefficients with respect to the aspherical surfaces. Note that “E−n”(n:integer) in each of the numerical values of the aspherical surfacecoefficients means “×10^(−n)”, and “E+n” therein means “×10^(n)”. Theaspherical surface coefficients are the values of respectivecoefficients KA, RBm (m=3, 4, 5, . . . 20) in the aspherical surfaceformula below:

Zd=C·h ²/{1+(1−KA·C ² ·h ²)^(1/2) }+ΣRBm·h ^(m)

where,Zd: the depth of an aspherical surface (the length of a perpendicularline drawn from a point on an aspherical surface with a height h to aplane perpendicular to the optical axis which contacts the peak of theaspherical surface)h: height (the distance from the optical axis to a lens surface)C: an inverse number of a paraxial radius of curvatureKA, RBm: aspherical surface coefficients (m=3, 4, 5, . . . 20).

In the various data, L (in Air) is the distance (back focus correspondsto an air converted length) from the object-side surface of the firstlens L1 to the imaging plane Sim along the optical axis Z, Bf (in Air)is the distance (which corresponds to back focus, the air convertedlength) from the image-side surface of the most-image-side lens to theimaging plane Sim along the optical axis Z, f is the focal length of theentire system, f1 is the focal length of the first lens L1, f2 is thefocal length of the second lens L2, f3 is the focal length of the thirdlens L3, f4 is the focal length of the fourth lens L4, f5 is the focallength of the fifth lens L5, f6 is the focal length of the sixth lensL6, f12 is the combined focal length of the first lens L1 and the secondlens L2, f34 is the combined focal length of the third lens L3 and thefourth lens L4, f56 is the combined focal length of the fifth lens L5and the sixth lens L6, f3456 is the combined focal length of the thirdlens L3, the fourth lens L4, the fifth lens L5 and the sixth lens L6.

Tables 16 and 17 collectively show values respectively corresponding tothe conditional formulas (1) through (15) of each Example. Note thatconditional formula (1) corresponds to f5/f, conditional formula (2)corresponds to R1/f, conditional formula (3) corresponds to f4/f5,conditional formula (4) corresponds to f56/f, conditional formula (5)corresponds to f34/f56, conditional formula (6) corresponds to f34/f,conditional formula (7) corresponds to f3456/f, conditional formula (8)corresponds to νd2/νd3, conditional formula (9) corresponds to f3/f,conditional formula (10) corresponds to f3/f4, conditional formula (11)corresponds to f12/f, conditional formula (12) corresponds to(Nd1+Nd2+Nd3+Nd4+Nd5+Nd6)/6, conditional formula (13) corresponds toL/f, conditional formula (14) corresponds to Bf/f, and conditionalformula (15) corresponds to (νd2+νd4+νd5)/3.

where,L: the distance (back focus corresponds to the air converted length)from the peak of the object-side surface of the first lens L1 to theimaging plane,Bf: the distance (an air converted length) from the peak of theimage-side surface of the sixth lens L6 to the imaging plane,R1: the radius of curvature of the object-side surface of the first lensL1,f: the focal length of the entire system,f1: the focal length of the first lens L1,f3: the focal length of the third lens L3,f4: the focal length of the fourth lens L4,f5: the focal length of the fifth lens L5,f12: the combined focal length of the first lens L1 and the second lensL2,f34: the combined focal length of the third lens L3 and the fourth lensL4,f56: the combined focal length of the fifth lens L5 and the sixth lensL6,f3456: the combined focal length of the third lens L3, the fourth lensL4, the fifth lensL15 and the sixth lens L6,Nd1 through Nd6: the refractive indices of the materials of the firstlens L1 through the sixth lens L6 with respect to the d-line,νd2: the Abbe number of the material of the second lens L2 with respectto the d-line,νd3: the Abbe number of the material of the third lens L3 with respectto the d-line,νd4: the Abbe number of the material of the fourth lens L4 with respectto the d-line, andνd5: the Abbe number of the material of the fifth lens L5 with respectto the d-line.

Regarding the unit of each numerical value, mm is used as the unit oflength, but this is only an example and other appropriate units may alsobe used, as optical systems are usable even when they are proportionallyenlarged or miniaturized.

TABLE 1 EXAMPLE 1 (A) Si Ri Di Ndj νdj GLASS 1 −16.0028 1.00005 1.589161.1 S-BAL35 2 3.1023 1.72148 3 9.5114 3.00019 1.8830 40.8 S-LAH58 4−5.4913 0.00002 5(St) ∞ 0.70000 *6 −4.3687 070000 1.6336 23.6 *7 11.01940.15000 *8 3.7836 2.18923 1.5339 56.0 9 −5.1610 0.20000 *10 47.83581.80007 1.5339 56.0 *11 −11.5322 0.50036 *12 −8.8380 0.70002 1.6336 23.613 ∞ 3.00000 14 ∞ 1.00000 1.5168 64.2 15 ∞ 0.41173 IMAGING PLANE (B)L(in Air) 16.7 Bf(in Air) 4.1 f 4.68 f1 −4.33 f2 4.35 f3 −4.85 f4 4.47f5 17.59 f6 −13.95 f12 6.46 f34 14.52 f56 −84.30 f3456 16.79 (C) SURFACENUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  4.5461595E−03 −4.6801135E−04−5.4733110E−04 −5.9052316E−05 7 0.0000000E+00  1.5793110E−03−2.2626274E−03 −3.2644487E−04  4.5376646E−04 8 −3.1504000E+00 −4.9541018E−03  3.8630852E−03 −2.0162564E−04 −1.4892261E−04 100.0000000E+00 −3.5018449E−04  8.4265693E−04 −2.7405436E−04−3.3738862E−04 11 0.0000000E+00 −7.0343776E−03  1.6960230E−03−1.8416642E−05 −1.6412146E−03 12 0.0000000E+00 −4.5147700E−03−3.7940482E−03 −2.5909004E−03 −5.9928496E−04 SURFACE NUMBER RB7 RB8 RB9RB10 6  8.3853951E−05 4.9787435E−05 −1.5545871E−05   3.0333532E−06 7 1.1092399E−04 −6.0919650E−05  7.7273291E−05 −1.4400348E−05 8−1.7330176E−06 3.8453547E−05 3.7180158E−07 −3.8938003E−06 10−2.6082230E−05 1.4375497E−04 11 −5.2906671E−04 4.9034938E−04 12 3.5669815E−05 8.5319892E−05

TABLE 2 EXAMPLE 2 (A) Si Ri Di Ndj νdj GLASS 1 −16.0233 1.00005 1.589161.1 S-BAL35 2 3.1453 1.64365 3 9.5311 3.00019 1.8830 40.8 S-LAH58 4−5.4755 0.00002 5(St) ∞ 0.70000 *6 −4.2210 0.70000 1.6336 23.6 *711.0450 0.15000 *8 3.7590 2.30000 1.5339 56.0 9 −5.1488 0.20000 *1031.8403 1.80007 1.5339 56.0 *11 −11.8978 0.50036 *12 −8.5603 0.700021.6336 23.6 13 ∞ 3.00000 14 ∞ 1.10000 1.5168 64.2 15 ∞ 0.37981 IMAGINGPLANE (B) L(in Air) 16.8 Bf(in Air) 4.1 f 4.76 f1 −4.38 f2 4.35 f3 −4.74f4 4.47 f5 16.46 f6 −13.51 f12 6.57 f34 14.98 f56 −104.69 f3456 16.59(C) SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  5.1355246E−03−3.5652299E−04 −5.3536977E−04 −6.3698863E−05 7 0.0000000E+00 1.7082451E−03 −2.2160942E−03 −3.2318111E−04  4.4896698E−04 8−3.1504000E+00  −5.0899737E−03  3.8242317E−03 −2.0522243E−04−1.4544310E−04 10 0.0000000E+00 −6.1454567E−04  7.7540717E−04−2.9340560E−04 −3.4211634E−04 11 0.0000000E+00 −7.0108481E−03 1.6601079E−03 −1.7823331E−05 −1.6380659E−03 12 0.0000000E+00−4.1825659E−03 −3.6552371E−03 −2.5602851E−03 −5.9012182E−04 SURFACENUMBER RB7 RB8 RB9 RB10 6 7.9993277E−05 4.7861831E−05 −1.4861770E−03  3.6095246E−06 7 8.4625108E−05 −5.2452017E−05  7.7273291E−05−1.4400348E−05 8 1.7126242E−06 4.0645575E−05 1.0787694E−06−4.2884376E−06 10 −3.1663199E−05  1.3851698E−04 11 −5.2956386E−04 4.8816991E−04 12 4.2203515E−05 9.1618032E−05

TABLE 3 EXAMPLE 3 (A) Si Ri Di Ndj νdj GLASS 1 −15.0107 1.00005 1.589161.1 S-BAL35 2 3.0422 1.68716 3 7.9319 3.00019 1.8830 40.8 S-LAH58 4−5.4959 0.00002 5(St) ∞ 0.70000 *6 −3.6033 0.70000 1.6336 23.6 *713.3327 0.15000 *8 3.8015 2.30004 1.5339 56.0 9 −4.3179 0.20000 *10−10000.0000 1.80007 1.5339 56.0 *11 −11.8194 0.50036 *12 −9.2974 0.700021.6336 23.6 13 ∞ 2.60000 14 ∞ 1.50000 1.5168 64.2 15 ∞ 0.35643 IMAGINGPLANE (B) L(in Air) 16.7 Bf(in Air) 3.9 f 4.63 f1 −4.21 f2 4.11 f3 −4.41f4 4.20 f5 22.16 f6 −14.67 f12 5.87 f34 12.62 f56 −46.53 f3456 17.21 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  7.7486443E−031.2716555E−03 −4.3336430E−04 −2.1760088E−04 7 0.0000000E+00 2.6789274E−03 −1.0103058E−03  −5.7293572E−04  1.9851144E−04 8−3.1504000E+00  −6.2026828E−03 2.7236052E−03 −3.0511802E−04−1.7179420E−04 10 0.0000000E+00 −1.1390821E−03 −1.1756415E−03 −9.1406236E−04 −4.8865070E−04 11 0.0000000E+00 −1.7517292E−031.3992760E−04  4.5056149E−04 −1.3115059E−03 12 0.0000000E+00−2.2858830E−03 1.3920545E−03 −1.9586408E−03 −7.2439547E−04 SURFACENUMBER RB7 RB8 RB9 RB10 6 −2.5513301E−05 −7.5523981E−06  −2.2859767E−051.6889624E−05 7 −1.4341074E−04 −1.6766734E−06   7.7273291E−05−1.4400348E−05  8 −3.0608921E−05 1.8431415E−05 −2.0068488E−061.4573847E−07 10 −4.9534555E−05 1.5848561E−04 11 −5.2267657E−043.9550621E−04 12 −1.4911200E−05 1.5513427E−04

TABLE 4 EXAMPLE 4 (A) Si Ri Di Ndj νdj GLASS 1 −15.0307 1.00005 1.589161.1 S-BAL35 2 3.1268 1.51747 3 7.7961 3.00019 1.8830 40.8 S-LAH58 4−5.4769 0.00002 5(St) ∞ 0.70000 *6 −4.2659 0.70000 1.6336 23.6 *7 9.01090.15000 *8 4.0102 2.30004 1.5339 56.0 9 −3.9299 0.20000 *10 −10000.00001.80007 1.5339 56.0 *11 −16.0005 0.50036 *12 −10.5053 0.70002 1.633623.6 13 ∞ 2.30000 14 ∞ 1.20000 1.5168 64.2 15 ∞ 0.64647 IMAGING PLANE(B) L(in Air) 16.3 Bf(in Air) 3.7 f 4.68 f1 −4.31 f2 4.08 f3 −4.48 f44.13 f5 30.02 f6 −16.58 f12 6.05 f34 11.42 f56 −38.47 f3456 16.19 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00 7.4926052E−031.1460193E−03 −1.8619950E−04 −6.0312019E−04 7 0.0000000E+001.1227733E−02 6.7701809E−04 −2.9358140E−03  1.7148372E−04 8−3.1504000E+00  7.1260395E−03 −5.0416075E−03  −2.8899716E−05−1.3726197E−04 10 0.0000000E+00 1.2950331E−03 2.4505233E−03 4.5322149E−05 −2.2864912E−04 11 0.0000000E+00 −8.8321408E−03 9.0509371E−03  7.2509657E−04 −2.0201209E−03 12 0.0000000E+00−2.0761457E−02  1.3916614E−02 −4.1334881E−03 −1.6031457E−03 SURFACENUMBER RB7 RB8 RB9 RB10 6 −8.7046884E−05 1.1334053E−05 −2.5468386E−06 8.7823398E−06 7  6.9277888E−04 −4.2248530E−04   7.7273291E−05−1.4400348E−05 8 −4.8767895E−05 1.6086385E−06 −1.4210755E−05−1.5652353E−05 10 −1.3859690E−06 1.4225855E−04 11 −8.2840469E−043.6787139E−04 12 −3.0480417E−04 6.3900004E−05

TABLE 5 EXAMPLE 5 (A) Si Ri Di Ndj νdj GLASS 1 −16.3949 1.00005 1.589161.1 S-BAL35 2 3.2572 1.68493 3 8.3055 3.00019 1.8830 40.8 S-LAH58 4−5.7302 0.00002 5(St) ∞ 0.68002 *6 −4.4415 0.70000 1.6336 23.6 *7 9.11180.15000 *8 3.9439 2.30004 1.5339 56.0 9 −4.0317 0.20000 *10 −10000.00001.80007 1.5339 56.0 *11 −12.4755 0.50037 *12 −8.8343 0.70000 1.6336 23.613 ∞ 3.00000 14 ∞ 0.50000 1.5168 64.2 15 ∞ 0.36647 IMAGING PLANE (B)L(in Air) 16.4 Bf(in Air) 3.7 f 4.63 f1 −4.53 f2 4.27 f3 −4.62 f4 4.15f5 23.39 f6 −13.94 f12 6.24 f34 11.11 f56 −36.43 f3456 15.68 (C) SURFACENUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  6.1685644E−03 3.7629714E−041.3294315E−04 −6.6272661E−04 7 0.0000000E+00  1.4902890E−032.0516194E−05 −2.8366138E−03   5.3871721E−04 8 −3.1504000E+00 −2.5747681E−03 −5.1166286E−03  3.9464087E−04 −1.2102856E−04 100.0000000E+00 −4.1549964E−05 4.4397957E−03 2.1703092E−04 −2.2253916E−0411 0.0000000E+00 −6.9812796E−03 9.6093236E−03 1.2503105E−03−2.0045277E−03 12 0.0000000E+00 −1.7871411E−02 1.4075293E−02−4.6420608E−03  −1.5497149E−03 SURFACE NUMBER RB7 RB8 RB9 RB10 6−1.0153078E−04 2.5123572E−05 1.6046661E−06  7.0006730E−06 7 6.1670732E−04 −4.1231674E−04  7.7273291E−05 −1.4400348E−05 8−4.4050934E−05 7.5969523E−06 −1.1478378E−05  −1.6073373E−05 10−3.0924771E−05 1.2146325E−04 11 −8.5740078E−04 3.6539968E−04 12−2.6000809E−04 9.5510122E−05

TABLE 6 EXAMPLE 6 (A) Si Ri Di Ndj νdj GLASS 1 −16.4518 1.00005 1.589161.1 S-BAL35 2 3.2368 1.72555 3 8.1572 3.00019 1.8830 40.8 S-LAH58 4−5.7689 0.00002 5(St) ∞ 0.68002 *6 −4.8649 0.70000 1.6336 23.6 *7 7.03130.15000 *8 3.7415 2.30004 1.5339 56.0 9 −4.0068 0.20000 *10 −10000.00001.80007 1.5339 56.0 *11 −13.4756 0.50037 *12 −9.1347 0.70000 1.6336 23.613 ∞ 2.90000 14 ∞ 0.55000 1.5168 64.2 15 ∞ 0.41914 IMAGING PLANE (B)L(in Air) 16.4 Bf(in Air) 3.7 f 4.63 f1 −4.51 f2 4.26 f3 −4.44 f4 4.04f5 25.27 f6 −14.42 f12 6.16 f34 11.20 f56 −35.18 f3456 16.16 (C) SURFACENUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  5.5874231E−03 −1.0065671E−031.9671317E−04 −6.4928315E−04 7 0.0000000E+00  1.3188541E−04−1.3372053E−03 −2.9735562E−03   5.5422930E−04 8 −3.1504000E+00 −3.2542152E−03 −4.5873432E−03 2.3104910E−04 −2.3219224E−04 100.0000000E+00  5.6261784E−04  4.2230406E−03 2.2290216E−04 −2.1074218E−0411 0.0000000E+00 −4.5301926E−03  9.2119493E−03 1.1385821E−03−2.0813184E−03 12 0.0000000E+00 −1.6428603E−02  1.4388018E−02−5.0293255E−03  −1.5891795E−03 SURFACE NUMBER RB7 RB8 RB9 RB10 6−9.2704708E−05 3.3852922E−05 3.4408043E−06  5.7233182E−06 7 5.4786705E−04 −3.7836793E−04  7.7273291E−05 −1.4400348E−05 8−6.7353535E−05 8.4539828E−06 −9.3218888E−06  −1.5462930E−05 10−2.9656625E−05 1.1965457E−04 11 −8.6447582E−04 3.7903492E−04 12−2.4484457E−04 1.1064799E−04

TABLE 7 EXAMPLE 7 (A) Si Ri Di Ndj νdj GLASS 1 −16.7519 1.00005 1.589161.1 S-BAL35 2 3.1819 1.77402 3 8.7837 3.00019 1.8830 40.8 S-LAH58 4−5.5932 0.00002 5(St) ∞ 0.70002 *6 −4.7070 0.70000 1.6336 23.6 *7 6.92010.15000 *8 3.8976 2.30004 1.5339 56.0 9 −3.8758 0.20000 *10 −100.00001.80007 1.5339 56.0 *11 −13.3441 0.60000 *12 −10.8851 0.70000 1.633623.6 13 ∞ 3.00000 14 ∞ 0.80000 1.5168 64.2 15 ∞ 0.39597 IMAGING PLANE(B) L(in Air) 16.8 Bf(in Air) 3.9 f 4.63 f1 −4.46 f2 4.29 f3 −4.32 f44.06 f5 28.64 f6 −17.18 f12 6.13 f34 11.69 f56 −44.58 f3456 15.78 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  7.3486246E−03−1.2947795E−03 3.8974350E−04 −8.0838337E−04 7 0.0000000E+00 3.9133637E−03 −1.2647512E−03 −2.9540091E−03   6.8598801E−04 8−3.1504000E+00  −3.8997767E−04 −6.3371585E−03 4.6621084E−04−2.0095408E−04 10 0.0000000E+00  1.4355894E−03  4.0679846E−032.4556746E−04 −1.8644191E−04 11 0.0000000E+00 −3.9758761E−03 8.7522017E−03 1.1477768E−03 −2.1753757E−03 12 0.0000000E+00−1.7107323E−02  1.5834935E−02 −5.5191782E−03  −1.6540216E−03 SURFACENUMBER RB7 RB8 RB9 RB10 6 −1.4103994E−04 4.1209943E−05 1.1850244E−05 5.2541751E−06 7  3.4314811E−04 −3.2364128E−04  7.7273291E−05−1.4400348E−05 8 −5.3512078E−05 2.1737292E−05 −2.3466717E−06 −1.9445456E−05 10 −5.4091890E−05 7.2523622E−05 11 −9.1311243E−043.6284502E−04 12 −2.3744740E−04 1.2690602E−04

TABLE 8 EXAMPLE 8 (A) Si Ri Di Ndj νdj GLASS 1 −16.6851 1.00005 1.589161.1 S-BAL35 2 3.1877 1.79562 3 8.8582 3.00019 1.8830 40.8 S-LAH58 4−5.6044 0.00002 5(St) ∞ 0.70002 *6 −4.7799 0.70000 1.6336 23.6 *7 6.93530.15000 *8 3.8606 2.30004 1.5339 56.0 9 −3.8664 0.20000 *10 −50.00001.80007 1.5339 56.0 *11 −12.5956 0.60000 *12 −10.8953 0.70000 1.633623.6 13 ∞ 3.00000 14 ∞ 0.80000 1.5168 64.2 15 ∞ 0.39636 IMAGING PLANE(B) L(in Air) 16.9 Bf(in Air) 3.9 f 4.63 f1 −4.46 f2 4.31 f3 −4.36 f44.04 f5 31.02 f6 −17.20 f12 6.14 f34 11.28 f56 −39.19 f3456 15.91 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  7.3584099E−03−1.2022179E−03 4.0079151E−04 −8.2307870E−04 7 0.0000000E+00 3.9563005E−03 −1.2729845E−03 −2.9471907E−03   6.8291800E−04 8−3.1504000E+00  −2.7538399E−04 −6.3373840E−03 4.5755584E−04−2.1379193E−04 10 0.0000000E+00  1.4926923E−03  4.0928341E−032.5325247E−04 −1.8118490E−04 11 0.0000000E+00 −3.8427540E−03 8.7714589E−03 1.1601513E−03 −2.1679564E−03 12 0.0000000E+00−1.7054863E−02  1.5814036E−02 −5.5230468E−03  −1.6491985E−03 SURFACENUMBER RB7 RB8 RB9 RB10 6 −1.5137045E−04 3.7956840E−05 1.2742579E−05 5.8945849E−06 7  3.1127315E−04 −3.1093561E−04  7.7273291E−05−1.4400348E−05 8 −6.0046989E−05 2.0460645E−05 −1.1620740E−06 −1.9212624E−05 10 −5.2702831E−05 7.2273602E−05 11 −9.1043567E−043.6249149E−04 12 −2.3465369E−04 1.2790563E−04

TABLE 9 EXAMPLE 9 (A) Si Ri Di Ndj νdj GLASS 1 −16.3898 1.00005 1.589161.1 S-BAL35 2 3.2332 1.70769 3 9.1787 3.00019 1.8830 40.8 S-LAH58 4−5.5515 0.00002 5(St) ∞ 0.70002 *6 −4.6887 0.70000 1.6336 23.6 *7 6.97760.15000 *8 3.8181 2.30004 1.5339 56.0 9 −3.8370 0.20000 *10 −50.00001.80007 1.5339 56.0 *11 −11.7003 0.60000 *12 −10.8067 0.70000 1.633623.6 13 ∞ 3.00000 14 ∞ 0.80000 1.5168 64.2 15 ∞ 0.41381 IMAGING PLANE(B) L(in Air) 16.8 Bf(in Air) 3.9 f 4.63 f1 −4.50 f2 4.33 f3 −4.33 f44.00 f5 28.15 f6 −17.06 f12 6.34 f34 11.12 f56 −44.27 f3456 14.84 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  7.0849026E−03−1.1161414E−03 4.1199411E−04 −8.4491010E−04 7 0.0000000E+00 3.8823009E−03 −1.3661888E−03 −2.9746520E−03   6.6917489E−04 8−3.1504000E+00  −1.4179684E−04 −6.3770267E−03 4.2527663E−04−2.4507134E−04 10 0.0000000E+00  1.4843454E−03  4.1513434E−032.7517207E−04 −1.6896413E−04 11 0.0000000E+00 −4.0326765E−03 8.7927260E−03 1.1829809E−03 −2.1535396E−03 12 0.0000000E+00−1.7022207E−02  1.5648395E−02 −5.5649359E−03  −1.6458331E−03 SURFACENUMBER RB7 RB8 RB9 RB10 6 −1.6439126E−04 3.5292725E−05 1.4339604E−05 8.1339637E−06 7  2.4382636E−04 −2.6634264E−04  7.7273291E−05−1.4400348E−05 8 −7.2971234E−05 2.0150563E−05 2.0998427E−06−1.7086546E−05 10 −4.6235487E−05 7.4795422E−05 11 −8.9978097E−043.7021554E−04 12 −2.2883928E−04 1.3067762E−04

TABLE 10 EXAMPLE 10 (A) Si Ri Di Ndj νdj GLASS 1 −17.1016 1.00005 1.589161.1 S-BAL35 2 3.1717 1.59333 3 8.6687 3.70000 1.8830 40.8 S-LAH58 4−5.4486 0.00002 5(St) ∞ 0.70002 *6 −5.2309 0.70000 1.6336 23.6 *7 7.11350.15000 *8 4.0188 2.30004 1.5339 56.0 9 −4.2339 0.20000 *10 −50.00001.80007 1.5339 56.0 *11 −12.0189 0.60000 *12 −12.0608 0.70002 1.633623.6 13 ∞ 3.00000 14 ∞ 1.00000 1.5168 64.2 15 ∞ 0.09153 IMAGING PLANE(B) L(in Air) 17.2 Bf(in Air) 3.8 f 4.63 f1 −4.46 f2 4.32 f3 −4.66 f44.28 f5 29.15 f6 −19.04 f12 6.01 f34 12.61 f56 −56.14 f3456 16.26 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00 3.6772145E−03−1.7394321E−03 5.0613802E−04 −7.7842783E−04 7 0.0000000E+001.8826424E−03 −1.6529237E−03 −3.0513283E−03   6.4270281E−04 8−3.1504000E+00  1.7270468E−03 −6.0662635E−03 6.3232117E−04−1.6781281E−04 10 0.0000000E+00 1.6111077E−03  3.7710753E−031.1186519E−04 −2.3094975E−04 11 0.0000000E+00 −3.2264468E−03  8.8080607E−03 1.1771203E−03 −2.1788291E−03 12 0.0000000E+00−1.6340241E−02   1.5962307E−02 −5.5481006E−03  −1.6271278E−03 SURFACENUMBER RB7 RB8 RB9 RB10 6 −1.3937288E−04 5.5792526E−05 7.2375511E−06 7.2180784E−06 7  2.5283385E−04 −1.6759346E−04  7.7273291E−05−1.4400348E−05 8 −3.5356384E−05 5.2235885E−05 1.3186518E−05−1.0937991E−05 10 −7.6821948E−05 3.9274522E−05 11 −9.1906575E−043.6106312E−04 12 −2.0117402E−04 1.6266229E−04

TABLE 11 EXAMPLE 11 (A) Si Ri Di Ndj νdj GLASS 1 −16.3017 1.00005 1.589161.1 S-BAL35 2 3.2620 1.66835 3 9.6106 3.00019 1.8830 40.8 S-LAH58 4−5.5020 0.00002 5(St) ∞ 0.70002 *6 −4.6259 0.70000 1.6336 23.6 *7 7.02210.15000 *8 3.8083 2.30004 1.5339 56.0 9 −3.8264 0.20000 *10 −50.00001.80007 1.5339 56.0 *11 −11.0661 0.60000 *12 −10.8159 0.70000 1.633623.6 13 ∞ 3.10000 14 ∞ 0.80000 1.5168 64.2 15 ∞ 0.38183 IMAGING PLANE(B) L(in Air) 16.8 Bf(in Air) 4.0 f 4.63 f1 −4.53 f2 4.37 f3 −4.30 f43.99 f5 26.20 f6 −17.07 f12 6.49 f34 11.12 f56 −50.50 f3456 14.21 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  6.9491169E−03−1.1665683E−03 3.8658669E−04 −8.5694348E−04 7 0.0000000E+00 3.7977043E−03 −1.4138100E−03 −2.9945546E−03   6.6171399E−04 8−3.1504000E+00  −7.5893210E−05 −6.3761889E−03 4.1837970E−04−2.5203552E−04 10 0.0000000E+00  1.4783705E−03  4.1839284E−032.8847223E−04 −1.6528467E−04 11 0.0000000E+00 −4.1870275E−03 8.7774782E−03 1.1809445E−03 −2.1519802E−03 12 0.0000000E+00−1.7090390E−02  1.5572234E−02 −5.5835232E−03  −1.6456988E−03 SURFACENUMBER RB7 RB8 RB9 RB10 6 −1.6694382E−04 3.6667459E−05 1.5605668E−05 8.6704854E−06 7  2.2575915E−04 −2.4805027E−04  7.7273291E−05−1.4400348E−05 8 −7.4024389E−05 2.2513143E−05 3.6260881E−06−1.6287053E−05 10 −4.7066044E−05 7.3698993E−05 11 −8.9626218E−043.7362965E−04 12 −2.2668273E−04 1.3207277E−04

TABLE 12 EXAMPLE 12 (A) Si Ri Di Ndj νdj GLASS 1 −17.2921 1.00005 1.589161.1 S-BAL35 2 3.3261 1.87115 3 8.9580 3.00019 1.8830 40.8 S-LAH58 4−5.9249 0.00002 5(St) ∞ 0.70002 *6 −4.7009 0.70000 1.6336 23.6 *7 7.22580.15000 *8 4.0101 2.30004 1.5339 56.0 9 −3.8689 0.20000 *10 −50.00001.80007 1.5339 56.0 *11 −10.1234 0.60000 *12 −10.7065 0.85001 1.633623.6 13 ∞ 2.60000 14 ∞ 1.40000 1.5168 64.2 15 ∞ 0.43949 IMAGING PLANE(B) L(in Air) 17.1 Bf(in Air) 4.0 f 4.63 f1 −4.65 f2 4.46 f3 −4.39 f44.11 f5 23.41 f6 −16.90 f12 6.44 f34 11.69 f56 −63.77 f3456 14.24 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  6.5812237E−03−1.2189329E−03 4.8783295E−04 −7.8831726E−04 7 0.0000000E+00 2.7020159E−03 −1.7092048E−03 −3.0943202E−03   6.5072984E−04 8−3.1504000E+00  −1.4588240E−03 −6.5566297E−03 4.1175512E−04−2.4602348E−04 10 0.0000000E+00  8.2650209E−04  3.7142052E−033.1747360E−05 −2.7156520E−04 11 0.0000000E+00 −4.9063869E−03 8.7327237E−03 1.3131993E−03 −2.0782929E−03 12 0.0000000E+00−1.7451774E−02  1.6748156E−02 −5.2063245E−03  −1.5297494E−03 SURFACENUMBER RB7 RB8 RB9 RB10 6 −1.3515414E−04 4.6788496E−05 1.1343604E−05 4.3658914E−06 7  2.7561256E−04 −2.3633081E−04  7.7273291E−05−1.4400348E−05 8 −6.7446332E−05 2.6374460E−05 5.1266328E−06−1.2959822E−05 10 −6.0626667E−05 9.0595940E−05 11 −8.5642581E−043.9971646E−04 12 −1.6125211E−04 1.8935400E−04

TABLE 13 EXAMPLE 13 (A) Si Ri Di Ndj νdj 1 −20.0340 1.00005 1.5168 64.2BSC7 2 3.1433 1.74010 3 8.7797 3.70000 1.8040 46.6 S-LAH65 4 −5.39770.00002 5(St) ∞ 0.70002 *6 −5.1254 0.70000 1.6140 25.5 *7 6.3925 0.15000*8 3.9735 2.48985 1.5110 55.2 9 −3.9427 0.20000 *10 50.4014 1.800071.5110 55.2 *11 −12.8445 0.60000 *12 −10.3810 0.70002 1.6140 25.5 13−300.0210 2.90000 14 ∞ 1.00000 1.5168 64.2 15 ∞ 0.12603 IMAGING PLANE(B) L(in Air) 17.5 Bf(in Air) 3.7 f 4.64 f1 −5.18 f2 4.70 f3 −4.53 f44.33 f5 20.22 f6 −17.53 f12 6.51 f34 13.03 f56 −189.92 f3456 13.44 (C)SURFACE NUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00 2.8737164E−03−1.8135350E−03  6.5475083E−04 −6.7213841E−04 7 0.0000000E+002.7920640E−03 −1.7457556E−03 −3.1385275E−03  6.6751302E−04 8−3.1504000E+00  2.0403883E−03 −5.8328022E−03  7.2045578E−04−1.4488120E−04 10 0.0000000E+00 1.0817327E−03  3.3856758E−03−1.9121692E−05 −2.5047474E−04 11 0.0000000E+00 −2.8442848E−03  9.1241463E−03  1.3037685E−03 −2.1372721E−03 12 0.0000000E+00−1.4577508E−02   1.6448269E−02 −5.3711862E−03 −1.5509112E−03 SURFACENUMBER RB7 RB8 RB9 RB10 6 −1.0170421E−04 5.8431400E−05 4.3849473E−08 3.9526003E−06 7  3.8456395E−04 −1.5544188E−04  7.7273291E−05−1.4400348E−05 8 −3.1035930E−05 5.1926396E−05 1.8758081E−05−6.8379671E−06 10 −6.4197725E−05 3.5909333E−05 11 −9.1333892E−043.6108992E−04 12 −1.6848553E−04 1.7698934E−04

TABLE 14 EXAMPLE 14 (A) Si Ri Di Ndj νdj 1 −16.4294 1.00005 1.6228 57.1S-BSM10 2 3.0668 1.73473 3 6.3805 3.70000 1.7550 52.3 S-YGH51 4 −5.60950.00002 5(St) ∞ 0.70002 *6 −10.3583 0.70000 1.6518 21.0 *7 8.73740.15000 *8 4.2311 2.30004 1.5339 56.0 9 −5.2195 0.20000 *10 −50.00001.80007 1.5339 56.0 *11 −22.1857 0.60000 *12 −9.9921 0.70002 1.6518 21.013 ∞ 2.60000 14 ∞ 1.00000 1.5168 64.2 15 ∞ 0.05292 IMAGING PLANE (B)L(in Air) 16.9 Bf(in Air) 3.3 f 4.63 f1 −4.07 f2 4.56 f3 −7.17 f4 4.78f5 73.05 f6 −15.33 f12 7.04 f34 9.91 f56 −19.30 f3456 17.90 (C) SURFACENUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00  1.1807208E−03 −2.2664654E−035.8505295E−04 −6.8157326E−04 7 0.0000000E+00 −1.6710377E−03−2.4163653E−03 −3.2115980E−03   6.0945995E−04 8 −3.1504000E+00  4.3131541E−04 −6.3534613E−03 5.2154368E−04 −1.8542540E−04 100.0000000E+00  1.1404314E−03  4.2902452E−03 1.9214242E−04 −2.2733727E−0411 0.0000000E+00 −3.4548071E−03  8.5786281E−03 1.1273543E−03−2.2078295E−03 12 0.0000000E+00 −1.8193550E−02  1.5554870E−02−5.6688848E−03  −1.6491960E−03 SURFACE NUMBER RB7 RB8 RB9 RB10 6−1.0460876E−04 5.4869859E−05 4.1855720E−07 −6.8002540E−07 7 2.6274261E−04 −1.6331070E−04  7.7273291E−05 −1.4400348E−05 8−3.0253078E−05 5.7547534E−05 1.7405484E−05 −9.3018294E−06 10−8.4713120E−05 3.6190757E−05 11 −9.3682461E−04 3.5757439E−04 12−1.9661625E−04 1.7440672E−04

TABLE 15 EXAMPLE 15 (A) Si Ri Di Ndj νdj 1 −40.0278 1.00005 1.7550 52.3S-YGH51 2 3.3804 1.49671 3 8.2877 3.70000 1.8348 42.7 S-LAH55 4 −5.47660.00002 5(St) ∞ 0.70002 *6 −5.6053 0.70000 1.6336 23.6 *7 7.3258 0.15000*8 3.8947 2.30004 1.5339 56.0 9 −4.1784 0.20000 *10 −50.0000 1.800071.5339 56.0 *11 −12.0111 0.60000 *12 −13.6641 0.70002 1.6336 23.6 13 ∞3.00000 14 ∞ 1.00000 1.5168 64.2 15 ∞ 0.35443 IMAGING PLANE (B) L(inAir) 17.4 Bf(in Air) 4.0 f 4.46 f1 −4.09 f2 4.50 f3 −4.91 f4 4.19 f529.13 f6 −21.57 f12 7.33 f34 10.78 f56 −85.71 f3456 12.19 (C) SURFACENUMBER KA RB3 RB4 RB5 RB6 6 0.0000000E+00 3.8444001E−03 −1.6880696E−034.9899074E−04 −7.9641989E−04 7 0.0000000E+00 1.7341693E−03−1.6781710E−03 −3.0495442E−03   6.4564541E−04 8 −3.1504000E+00 1.9672471E−03 −6.0058823E−03 6.4641903E−04 −1.6514924E−04 100.0000000E+00 1.6253022E−03  3.7470140E−03 1.0399510E−04 −2.3240832E−0411 0.0000000E+00 −3.1467182E−03   8.8404977E−03 1.1857220E−03−2.1783468E−03 12 0.0000000E+00 −1.6224325E−02   1.5873470E−02−5.5682903E−03  −1.6239146E−03 SURFACE NUMBER RB7 RB8 RB9 RB10 6−1.5393923E−04 4.6680872E−05 4.2993358E−06  7.4751279E−06 7 2.6349095E−04 −1.7523183E−04  7.7273291E−05 −1.4400348E−05 8−3.5178468E−05 5.1998701E−05 1.3371904E−05 −1.0188984E−05 10−7.5074868E−05 3.8040097E−05 11 −9.1765037E−04 3.6108998E−04 12−1.9936153E−04 1.6151910E−04

TABLE 16 CONDITIONAL FORMULAS (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)EXAMPLES f5/f R1/f f4/f5 f56/f f34/f56 f34/f f3456/f vd2/vd3 f3/f f3/f41 3.76 −3.42 0.25 −18.02 −0.17 3.10 3.59 1.73 −1.04 −1.09 2 3.46 −3.370.27 −21.99 −0.14 3.15 3.48 1.73 −0.99 −1.06 3 4.79 −3.24 0.19 −10.05−0.27 2.73 3.72 1.73 −0.95 −1.05 4 6.42 −3.21 0.14 −8.22 −0.30 2.44 3.461.73 −0.96 −1.08 5 5.05 −3.54 0.18 −7.87 −0.30 2.40 3.39 1.73 −1.00−1.11 6 5.46 −3.55 0.16 −7.60 −0.32 2.42 3.49 1.73 −0.96 −1.10 7 6.19−3.62 0.14 −9.63 −0.26 2.52 3.41 1.73 −0.93 −1.06 8 6.70 −3.60 0.13−8.46 −0.29 2.44 3.44 1.73 −0.94 −1.08 9 6.08 −3.54 0.14 −9.56 −0.252.40 3.20 1.73 −0.93 −1.08 10 6.30 −3.70 0.15 −12.14 −0.22 2.73 3.511.73 −1.01 −1.09 11 5.66 −3.52 0.15 −10.91 −0.22 2.40 3.07 1.73 −0.93−1.08 12 5.05 −3.73 0.18 −13.77 −0.18 2.53 3.07 1.73 −0.95 −1.07 13 4.36−4.32 0.21 −40.91 −0.07 2.81 2.90 1.82 −0.98 −1.04 14 15.79 −3.55 0.07−4.17 −0.51 2.14 3.87 2.49 −1.55 −1.50 15 6.53 −8.98 0.14 −19.22 −0.132.42 2.73 1.81 −1.10 −1.17

TABLE 17 CONDITIONAL FORMULAS (12) (15) (11) (Nd1 + Nd2 + Nd3 + (13)(14) (vd2 + EXAMPLES f12/f Nd4 + Nd5 + Nd6)/6 L/f Bf/f vd4 + vd5)/3 11.38 1.63 3.58 0.87 50.93 2 1.38 1.63 3.53 0.86 50.93 3 1.27 1.63 3.600.85 50.93 4 1.29 1.63 3.49 0.80 50.93 5 1.35 1.63 3.54 0.80 50.93 61.33 1.63 3.55 0.80 50.93 7 1.32 1.63 3.64 0.85 50.93 8 1.33 1.63 3.640.85 50.93 9 1.37 1.63 3.63 0.85 50.93 10 1.30 1.63 3.72 0.81 50.93 111.40 1.63 3.64 0.87 50.93 12 1.39 1.63 3.70 0.86 50.93 13 1.40 1.60 3.760.79 52.32 14 1.52 1.62 3.65 0.72 54.77 15 1.64 1.65 3.89 0.90 51.57

In the imaging lenses of Example 1 through 15 above, the first lens L1and the second lens L2 are glass spherical lenses, and the third lens L3through the sixth lens L6 are plastic aspherical lenses. Note that basiclens data indicates the names of the materials of the first lens L1 andthe second lens L2. For example, S-BAL35 by Ohara Corp. is indicated asthe material of the first lens L1 of Examples 1 through 12 in the basiclens data. However, glass materials by other companies having the samecharacteristics may be employed instead. For example, BACD5 by HOYA Co.,Ltd., K-SK5 by Sumita, H-ZK3 by Chengdu Guangming Co., and the like maybe employed instead of S-BAL35 by Ohara Co. Further, S-LAH 58 by OharaCo. is indicated as the material of the second lens L2 of each ofExamples 1 through 12. However, TAFD30 by HOYA Co., Ltd., K-LASFN17 bySumita and H-ZLAF68 by Chengdu Guangming Co. may be employed instead ofS-LAH 58 by Ohara Co.

Further, BSC7 by HOYA Co., Ltd. is indicated as the material of thefirst lens L1 of Example 13. However, S-BSL7 by Ohara Corp., K-BK7 bySumita, H-K9L by Chengdu Guangming Co., and N-BK7 by Schott may beemployed instead of BSC7 by HOYA Co., Ltd. Further, S-LAH65 by OharaCorp. is indicated as the material of the second lens L2 of Example 13.However, TAF3 by HOYA Co., Ltd., K-LASFN6 by Sumita, H-ZLAF50B byChengdu Guangming Co., and the like may be employed instead of S-LAH65by Ohara Corp.

Further, Ohara Corp. S-BSM10 is indicated as the material of the firstlens L1 of Example 14. However, E-BACD10 by HOYA Co., Ltd. and H-ZK10 byChengdu Guangming Co. may be employed instead of S-BSM10 by Ohara Corp.Further, S-YGH51 by Ohara Corp. is indicated as the material of thesecond lens L2 of Example 14 and the first lens L1 of Example 15.However, TACE by HOYA Co., Ltd., K-LASKN1 by Sumita, H-LAK53A by ChengduGuangming Co., and the like may be employed instead of S-YGH51 by OharaCorp. Further, S-LAH55 by Ohara Corp. is indicated as the material ofthe second lens L2 of Example 15. However, TAFD5F by HOYA Co., Ltd.,K-LASKN8 by Sumita, H-ZLAF55A by Chengdu Guangming Co., and the like maybe employed instead of S-LAH55 by Ohara Corp.

[Aberration Performance]

The respective aberration diagrams of the imaging lenses according toExamples 1 through 15 above are shown in A through D of FIG. 18, Athrough D of FIG. 19, A through D of FIG. 20, A through D of FIG. 21, Athrough D of FIG. 22, A through D of FIG. 23, A through D of FIG. 24, Athrough D of FIG. 25, A through D of FIG. 26, A through D of FIG. 27, Athrough D of FIG. 28, A through D of FIG. 29, A through D of FIG. 30, Athrough D of FIG. 31 and A through D of FIG. 32.

Here, the aberration diagram of Example 1 will be described as anexample. The same applies to the aberration diagrams of the otherExamples. A, B, C and D of FIG. 18 respectively show the aberrationdiagrams of spherical aberration, astigmatism, distortion, and lateralchromatic aberration of the imaging lens according to Example 1. F ineach of spherical aberrations refers to a F value, ω in each of theother aberration diagrams refers to a half angle of view. Distortiondiagrams show the amount of displacement from an ideal image heightwhich is f×tan (φ) by using the focal length f of the entire system andan angle of view φ (which is a variable, 0≦φ<ω). Each aberration diagramshows aberration with respect to the d-line (wavelength: 587.56 nm) asthe reference wavelength. The spherical aberration diagram also showsaberrations with respect to the F-line (wavelength: 486.13), the C-line(wavelength: 656.27 nm), the s-line (wavelength: 852.11 nm) andaberration with respect to the offense against the sine condition(denoted as SNC). The lateral chromatic aberration diagram also showsaberrations with respect to the F-line, the C-line, and the s-line. Thetypes of lines in the lateral chromatic aberration diagram are the sameas those in the spherical aberration diagram. Accordingly, redundantdescriptions thereof will be omitted.

As can be found from the data described above, each of the imaginglenses of Examples 1 through 15 is constituted by the small number oflenses, i.e., six lenses; and can be produced in a small size and at lowcost. The respective imaging lenses further have F numbers of between1.8 and 2.0 which are small, and have high optical performance with eachaberration corrected favorably. These imaging lenses can be suitablyused for surveillance cameras, vehicle mounted cameras for photographingimages in the front, side, and back of an automobile, and the like.

[Embodiment of the Imaging Apparatus]

FIG. 33 shows the aspect of an automobile 100 on which the imagingapparatus provided with the imaging lens of the present embodiment ismounted, as a usage example. In FIG. 33, the automobile 100 is providedwith an outside-vehicle camera 101 for photographing a blind angle rangeon the side surface of the passenger's side thereof, an outside-vehiclecamera 102 for photographing a blind angle range behind the automobile100, and an in-vehicle camera 103, which is provided on the back of aroom mirror, for photographing the same visual field range as thedriver's. The outside-vehicle cameras 101, 102 and the in-vehicle camera103 correspond to the imaging apparatus according to the embodiment ofthe present invention, and are provided with the imaging lens accordingto the present embodiment of the present invention and an imagingelement which converts an optical image formed by the imaging lens intoan electric signal.

All the imaging lenses according to the Examples of the presentinvention have the advantageous points described above. Accordingly, theoutside-vehicle cameras 101, 102 and the in-vehicle camera 103 can bealso configured in a small size and at low costs, have wider angles ofview, and enables fine images to be obtained through the peripheralportions of the imaging area.

The present invention has been described with reference to theEmbodiments and Examples. The present invention is not limited to theembodiments and the examples described above, and various modificationsare possible. For example, values, such as the radius of curvature, thedistances between surfaces, the refractive indices, the Abbe numbers ofeach lens element, and the like are not limited to the values in thenumerical examples shown in the Tables, but may be other values.

Note that all of the lenses of the Examples above are constituted byhomogeneous materials. However, gradient index lenses may be used as thelenses. Further, in some of the Examples above, the second lens L2through the sixth lens L6 are constituted by diffractive lenses in whichsurfaces are made aspherical. A diffractive optical element may beformed in one surface or a plurality of surfaces.

The embodiment of the imaging apparatus was described with reference tothe Figure of an example, in which the present invention is applied to avehicle mounted camera. The present invention is not limited to thisapplication and can be applied to portable terminal cameras,surveillance cameras, and the like, for example.

What is claimed is:
 1. An imaging lens consisting essentially of a firstlens having a negative power, a second lens having a positive power, athird lens having a negative power, a fourth lens having a positivepower, a fifth lens having a positive power, and a sixth lens having anegative power in this order from the object side, wherein the Abbenumber of the material of the third lens with respect to the d-line isless than or equal to 35, the Abbe number of the material of the sixthlens with respect to the d-line is less than or equal to 32, and theimaging lens satisfies conditional formula (1) below:2.38<f5/f  (1), where f: the focal length of the entire system, and f5:the focal length of the fifth lens.
 2. An imaging lens consistingessentially of a first lens having a negative power, a second lenshaving a positive power, a third lens having a negative power, a fourthlens having a positive power, a fifth lens having a positive power, anda sixth lens having a negative power in this order from the object side,wherein an aperture stop is disposed more toward the object side thanthe image-side surface of the fourth lens, the Abbe number of thematerial of the third lens with respect to the d-line is less than orequal to 35, the Abbe number of the material of the sixth lens withrespect to the d-line is less than or equal to 32, and the imaging lenssatisfies conditional formula (2) below:−4.1<R1/f<0.0  (2), where f: the focal length of the entire system, andR1: the radius of curvature of the object-side surface of the firstlens.
 3. An imaging lens consisting essentially of a first lens having anegative power, a second lens having a positive power, a third lenshaving a negative power, a fourth lens having a positive power, a fifthlens having a positive power, and a sixth lens having a negative powerin this order from the object side, wherein an aperture stop is disposedmore toward the object side than the image-side surface of the fourthlens, the Abbe number of the material of the third lens with respect tothe d-line is less than or equal to 35, the Abbe number of the materialof the sixth lens with respect to the d-line is less than or equal to32, and the imaging lens satisfies conditional formula (3) below:0<f4/f5<0.45  (3), where f4: the focal length of the fourth lens, andf5: the focal length of the fifth lens.
 4. The imaging lens of claim 1,wherein materials of the third lens, the fourth lens, the fifth lens,and the sixth lens are plastics.
 5. The imaging lens of claim 4 thatsatisfies conditional formula (7) below:2.0<f3456/f  (7), where f3456: the combined focal length of the thirdlens, the fourth lens, the fifth lens, and the sixth lens.
 6. Theimaging lens of claim 1 that satisfies conditional formula (8) below:0.9<νd2/νd3  (8), where νd2: the Abbe number of the material of thesecond lens with respect to the d-line, and νd3: the Abbe number of thematerial of the third lens with respect to the d-line.
 7. The imaginglens of claim 1 that satisfies conditional formula (9) below:−2.5<f3/f<−0.5  (9), where f: the focal length of the entire system, andf3: the focal length of the third lens.
 8. The imaging lens of claim 1,wherein the aperture stop is provided between the object-side surface ofthe second lens and the image-side surface of the fourth lens.
 9. Theimaging lens of claim 1 that satisfies conditional formula (10) below:−3.0<f3/f4<−0.2  (10), where f3: the focal length of the third lens, andf4: the focal length of the fourth lens.
 10. The imaging lens of claim 1that satisfies conditional formula (11) below:0.2<f12/f<5.0  (11), where f: the focal length of the entire system, andf12: the combined focal length of the first lens and the second lens.11. The imaging lens of claim 1 that satisfies conditional formula (12)below:(Nd1+Nd2+Nd3+Nd4+Nd5+Nd6)/6<1.70  (12), where Nd1 through Nd6: therefractive indices of the materials of the first lens through the sixthlens with respect to the d-line.
 12. The imaging lens of claim 1,wherein the object-side surface of the fourth lens is an asphericalsurface, both of the center and the edge of the effective diameter havepositive powers, and the positive power at the edge of the effectivediameter is weaker than that of the center.
 13. The imaging lens ofclaim 1, wherein the Abbe number of the material of the first lens withrespect to the d-line is greater than or equal to
 40. 14. The imaginglens of claim 1, wherein the Abbe number of the material of the secondlens with respect to the d-line is greater than or equal to
 25. 15. Theimaging lens of claim 1, wherein the Abbe number of the material of thefourth lens with respect to the d-line is greater than or equal to 40.16. The imaging lens of claim 1, wherein the Abbe number of the materialof the fifth lens with respect to the d-line is greater than or equal to40.
 17. The imaging lens of claim 1 that satisfies conditional formula(1-1) below:2.5<f5/f<20.0  (1-1), where f: the focal length of the entire system,and f5: the focal length of the fifth lens.
 18. The imaging lens ofclaim 1 that satisfies conditional formula (1-2) below:3.0<f5/f<17.0  (1-2), where f: the focal length of the entire system,and f5: the focal length of the fifth lens.
 19. The imaging lens ofclaim 1 that satisfies conditional formula (1-3) below:3.2<f5/f<17.0  (1-3), where f: the focal length of the entire system,and f5: the focal length of the fifth lens.
 20. An imaging apparatuscomprising: an imaging lens of claim 1.